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Cisco Security Advisory: IOS Heap-based Overflow Vulnerability in System Timers

  • From: Cisco Systems Product Security Incident Response Team
  • Date: Wed Nov 02 12:07:50 2005
  • Prevent-nondelivery-report:

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Hash: SHA1

Cisco Security Advisory: 
========================
IOS Heap-based Overflow Vulnerability in System Timers
======================================================

Document ID: 68064

Revision 1.0

For Public Release 2005 November 2 1600 UTC (GMT)

- -----------------------------------------------------------------------

Contents
========

    Summary
    Affected Products
    Background Information Regarding Heap Overflows
    Details
    Impact
    Software Versions and Fixes
    Obtaining Fixed Software
    Workarounds
    Exploitation and Public Announcements
    Status of This Notice: FINAL
    Distribution
    Revision History
    Cisco Security Procedures

- -----------------------------------------------------------------------

Summary
=======

The Cisco Internetwork Operating System (IOS) may permit arbitrary code
execution after exploitation of a heap-based buffer overflow
vulnerability. Cisco has included additional integrity checks in its
software, as further described below, that are intended to reduce the
likelihood of arbitrary code execution.

Cisco has made free software available that includes the additional
integrity checks for affected customers.

This advisory is posted at 
http://www.cisco.com/warp/public/707/cisco-sa-20051102-timers.shtml.

Cisco is not aware of any active exploitation of this vulnerability.
This advisory documents changes to Cisco IOS? as a result of continued
research related to the demonstration of the exploit for another
vulnerability which occurred in July 2005 at the Black Hat USA
Conference. Cisco addressed the IPv6 attack vector used in that
demonstration in a separate advisory published on July 29, 2005.

Affected Products
=================

This security advisory applies to all Cisco products that run Cisco IOS
Software. Any version of Cisco IOS prior to the versions listed in the
Fixed Software table below may be susceptible to heap overflow
exploitation.

Cisco IOS XR is not affected.

To determine the software running on a Cisco product, log in to the
device and issue the "show version" command to display the system banner.
Cisco IOS Software will identify itself as "Internetwork Operating
System Software" or simply "IOS". On the next line of output, the image
name will be displayed between parentheses, followed by "Version" and
the IOS release name. Other Cisco devices will not have the 
"show version" command or will give different output.

The following example identifies a Cisco product running IOS release
12.3(6) with an installed image name of C3640-I-M:

    Cisco Internetwork Operating System Software
    IOS (tm) 3600 Software (C3640-I-M), Version 12.3(6), RELEASE SOFTWARE (fc3)


The next example shows a product running IOS release 12.3(11)T3 with an
image name of C3845-ADVIPSERVICESK9-M:

    Cisco IOS Software, 3800 Software (C3845-ADVIPSERVICESK9-M), Version 12.3(11)T3, RELEASE SOFTWARE (fc4)
    Technical Support: http://www.cisco.com/techsupport
    Copyright (c) 1986-2005 by Cisco Systems, Inc.


Additional information about Cisco IOS release naming can be found at
http://www.cisco.com/warp/public/620/1.html.

No other Cisco products are currently known to be affected by the
vulnerability addressed in this advisory.

Background Information Regarding Heap Overflows
===============================================

As this security advisory pertains to heap overflows, the following
additional information is provided to aid in understanding the
terminology used in this advisory.

RFC 2828 defines a vulnerability as "A flaw or weakness in a system's
design, implementation, or operation and management that could be
exploited to violate the system's security policy." The threat from any
particular vulnerability in a system or a protocol depends on the ease
and likelihood in which the normal operations of a system can be
disrupted or compromised. In order to minimize the threat, each
possible attack vector for a particular vulnerability should either be
mitigated with protections which may prevent the circumstances required
for exploitation or remediated with software that no longer contains
the vulnerability.

Many forms of malicious software, commonly known as "exploits", contain
a payload that seeks to disrupt or compromise a system delivered
through well-known attack vectors for particular vulnerabilities. In
cases where it is likely that unpatched vulnerable systems exist,
counter-measures are often employed to attempt to block any and all
attack vectors to minimize the threat of successful exploitation. One
popular attack method often found in the payload of exploits is known
as a buffer overflow.

A heap-based overflow is a type of buffer overflow against a data
structure residing within the memory heap. The memory heap is a section
of system memory used by the operating system of the device to satisfy
the dynamic data storage requirements for currently running processes.
In a successful heap-based overflow, the operating system fails to
enforce bounds checking on a buffer, thus allowing for the possibility
of overwriting adjacent locations in system memory.

The threat from buffer overflows, like the one described in this
advisory, may be remediated in multiple ways. One way is to remove the
particular attack vector so that it no longer exists. Another way is to
employ protections in the underlying system to minimize the
consequences of any future buffer overflow vulnerabilities that may be
discovered.

Details
=======

Cisco IOS may be susceptible to remote code execution through attack
vectors such as specific heap-based overflows in which internal
operating system timers may execute arbitrary code from portions of
memory that have been overwritten via exploitation.

In many cases, a heap-based overflow in Cisco IOS will simply corrupt
system memory and trigger a system reload when detected by the "Check
Heaps" process, which constantly monitors for such memory corruption.
In a successful attack against an appropriate heap-based overflow, it
is possible to achieve code execution without the device crashing
immediately.

Cisco has devised counter-measures by implementing extra checks to
enforce the proper integrity of system timers. This extra validation
should reduce the possibility of heap-based overflow attack vectors
achieving remote code execution.

These improvements have been documented in Cisco Bug ID CSCei61732. 


Impact
======

Successful exploitations of heap-based buffer overflow vulnerabilities
in Cisco IOS software often result in a Denial of Service because the
exploit causes the router to crash and reload due to inconsistencies in
running memory. In some cases it is possible to overwrite areas of
system memory and execute arbitrary code from those locations. In the
event of successful remote code execution, device integrity will have
been completely compromised.

Software Versions and Fixes
===========================

When considering software upgrades, please also consult 
http://www.cisco.com/en/US/products/products_security_advisories_listing.html
and any subsequent advisories to determine exposure and a complete
upgrade solution.

In all cases, customers should exercise caution to be certain the
devices to be upgraded contain sufficient memory and that current
hardware and software configurations will continue to be supported
properly by the new release. If the information is not clear, contact
the Cisco Technical Assistance Center ("TAC") for assistance.

Each row of the Cisco IOS software table (below) describes a release
train and the platforms or products for which it is intended. If a
given release train is vulnerable, then the earliest possible releases
that contain the fix (the "First Fixed Release") and the anticipated
date of availability for each are listed in the "Rebuild" and
"Maintenance" columns. A device running a release in the given train
that is earlier than the release in a specific column (less than the
First Fixed Release) is known to be vulnerable. The release should be
upgraded at least to the indicated release or a later version (greater
than or equal to the First Fixed Release label).

For further information on the terms "Rebuild" and "Maintenance,"
please consult the following URL: 
http://www.cisco.com/warp/public/620/1.html.

+------------------------------------------------------+
|   Major    |    Availability of Repaired Releases    |
|  Release   |                                         |
|------------+-----------------------------------------|
|  Affected  |                    |                    |
| 12.0-Based |      Rebuild       |    Maintenance     |
|  Release   |                    |                    |
|------------+--------------------+--------------------|
| 12.0       | 12.0(28d)          |                    |
|------------+-----------------------------------------|
| 12.0DA     | Vulnerable; migrate to 12.2(12)DA9 or   |
|            | later                                   |
|------------+-----------------------------------------|
| 12.0DB     | Vulnerable; migrate to 12.3(14)T4 or    |
|            | later                                   |
|------------+-----------------------------------------|
| 12.0DC     | Vulnerable; migrate to 12.2(15)BC2i or  |
|            | later                                   |
|------------+-----------------------------------------|
|            | 12.0(28)S5         |                    |
|            |--------------------+--------------------|
| 12.0S      | 12.0(30)S4         |                    |
|            |--------------------+--------------------|
|            | 12.0(31)S1         |                    |
|------------+-----------------------------------------|
| 12.0SC     | Vulnerable; migrate to 12.2(15)BC2i or  |
|            | later                                   |
|------------+-----------------------------------------|
| 12.0SL     | Vulnerable; migrate to 12.0(31)S1 or    |
|            | later                                   |
|------------+-----------------------------------------|
| 12.0SP     | Vulnerable; migrate to 12.0(31)S1 or    |
|            | later                                   |
|------------+-----------------------------------------|
| 12.0ST     | Vulnerable; migrate to 12.0(31)S1 or    |
|            | later                                   |
|------------+-----------------------------------------|
| 12.0SX     | Vulnerable; contact TAC                 |
|------------+-----------------------------------------|
| 12.0SZ     | Vulnerable; migrate to 12.0(31)S1 or    |
|            | later                                   |
|------------+-----------------------------------------|
| 12.0T      | Vulnerable; migrate to 12.1(27b) or     |
|            | later                                   |
|------------+-----------------------------------------|
|            | 12.0(25)W5-27d     |                    |
|            |--------------------+--------------------|
| 12.0W5     | 12.0(28)W5-30b     |                    |
|            |--------------------+--------------------|
|            | 12.0(28)W5-32a     |                    |
|------------+--------------------+--------------------|
| 12.0WC     | 12.0(5)WC13        |                    |
|------------+-----------------------------------------|
| 12.0XA     | Vulnerable; migrate to 12.1(27b) or     |
|            | later                                   |
|------------+-----------------------------------------|
| 12.0XB     | Vulnerable; migrate to 12.1(27b) or     |
|            | later                                   |
|------------+-----------------------------------------|
| 12.0XC     | Vulnerable; migrate to 12.1(27b) or     |
|            | later                                   |
|------------+-----------------------------------------|
| 12.0XD     | Vulnerable; migrate to 12.1(27b) or     |
|            | later                                   |
|------------+-----------------------------------------|
| 12.0XE     | Vulnerable; migrate to 12.1(26)E3 or    |
|            | later                                   |
|------------+-----------------------------------------|
| 12.0XF     | Vulnerable; migrate to 12.1(27b) or     |
|            | later                                   |
|------------+-----------------------------------------|
| 12.0XG     | Vulnerable; migrate to 12.1(27b) or     |
|            | later                                   |
|------------+-----------------------------------------|
| 12.0XH     | Vulnerable; migrate to 12.1(27b) or     |
|            | later                                   |
|------------+-----------------------------------------|
| 12.0XI     | Vulnerable; migrate to 12.1(27b) or     |
|            | later                                   |
|------------+-----------------------------------------|
| 12.0XJ     | Vulnerable; migrate to 12.1(27b) or     |
|            | later                                   |
|------------+-----------------------------------------|
| 12.0XK     | Vulnerable; migrate to 12.2(31) or      |
|            | later                                   |
|------------+-----------------------------------------|
| 12.0XL     | Vulnerable; migrate to 12.2(31) or      |
|            | later                                   |
|------------+-----------------------------------------|
| 12.0XM     | Vulnerable; migrate to 12.1(27b) or     |
|            | later                                   |
|------------+-----------------------------------------|
| 12.0XN     | Vulnerable; migrate to 12.1(27b) or     |
|            | later                                   |
|------------+-----------------------------------------|
| 12.0XQ     | Vulnerable; migrate to 12.1(27b) or     |
|            | later                                   |
|------------+-----------------------------------------|
| 12.0XR     | Vulnerable; migrate to 12.2(31) or      |
|            | later                                   |
|------------+-----------------------------------------|
| 12.0XS     | Vulnerable; migrate to 12.1(26)E3 or    |
|            | later                                   |
|------------+-----------------------------------------|
| 12.0XV     | Vulnerable; migrate to 12.1(27b) or     |
|            | later                                   |
|------------+-----------------------------------------|
| Affected   |                    |                    |
| 12.1-Based | Rebuild            | Maintenance        |
| Release    |                    |                    |
|------------+--------------------+--------------------|
| 12.1       | 12.1(27b)          |                    |
|------------+-----------------------------------------|
| 12.1AA     | Vulnerable; migrate to 12.2(31) or      |
|            | later                                   |
|------------+-----------------------------------------|
|            | Vulnerable; for c3750-ME, migrate to    |
| 12.1AX     | 12.2(25)EY3 or later. For c2970 and     |
|            | 3750, migrate to 12.2(25)SEB4, 12.2(25) |
|            | SEC2, 12.2(25)SED or later.             |
|------------+-----------------------------------------|
| 12.1AY     | Vulnerable; migrate to 12.1(22)EA4a,    |
|            | 12.1(22)EA5a, 12.2(22)EA6 or later      |
|------------+-----------------------------------------|
| 12.1AZ     | Vulnerable; migrate to 12.1(22)EA4a,    |
|            | 12.1(22)EA5a, 12.2(22)EA6 or later      |
|------------+-----------------------------------------|
| 12.1CX     | Vulnerable; migrate to 12.2(31) or      |
|            | later                                   |
|------------+-----------------------------------------|
| 12.1DA     | Vulnerable; migrate to 12.2(12)DA9 or   |
|            | later                                   |
|------------+-----------------------------------------|
| 12.1DB     | Vulnerable; migrate to 12.3(14)T4 or    |
|            | later                                   |
|------------+-----------------------------------------|
| 12.1DC     | Vulnerable; migrate to 12.3(14)T4 or    |
|            | later                                   |
|------------+-----------------------------------------|
|            | 12.1(8b)E20        |                    |
|            |--------------------+--------------------|
|            | 12.1(13)E17        |                    |
| 12.1E      |--------------------+--------------------|
|            | 12.1(23)E4         |                    |
|            |--------------------+--------------------|
|            | 12.1(26)E3         |                    |
|------------+--------------------+--------------------|
|            | 12.1(22)EA4a       | 12.1(22)EA6        |
| 12.1EA     |--------------------+--------------------|
|            | 12.1(22)EA5a       |                    |
|------------+--------------------+--------------------|
| 12.1EB     | 12.1(26)EB1        |                    |
|------------+-----------------------------------------|
| 12.1EC     | Vulnerable; migrate to 12.2(15)BC2i or  |
|            | later                                   |
|------------+-----------------------------------------|
| 12.1EO     | 12.1(20)EO3,       |                    |
|            | available 11/30/05 |                    |
|------------+-----------------------------------------|
| 12.1EU     | Vulnerable; migrate to 12.2(20)EU2 or   |
|            | later                                   |
|------------+-----------------------------------------|
| 12.1EV     | Vulnerable; migrate to 12.2(26)SV1 or   |
|            | later                                   |
|------------+-----------------------------------------|
|            | 12.1(12c)EW4       |                    |
|            |--------------------+--------------------|
|            | 12.1(13)EW4        |                    |
| 12.1EW     |--------------------+--------------------|
|            | 12.1(19)EW3        |                    |
|            |--------------------+--------------------|
|            | 12.1(20)EW4        |                    |
|------------+-----------------------------------------|
| 12.1EX     | Vulnerable; migrate to 12.1(26)E3 or    |
|            | later                                   |
|------------+-----------------------------------------|
| 12.1EY     | Vulnerable; migrate to 12.1(26)E3 or    |
|            | later                                   |
|------------+-----------------------------------------|
| 12.1EZ     | Vulnerable; migrate to 12.1(26)E3 or    |
|            | later                                   |
|------------+-----------------------------------------|
| 12.1T      | Vulnerable; migrate to 12.2(31) or      |
|            | later                                   |
|------------+-----------------------------------------|
| 12.1XA     | Vulnerable; migrate to 12.2(31) or      |
|            | later                                   |
|------------+-----------------------------------------|
| 12.1XB     | Vulnerable; migrate to 12.2(31) or      |
|            | later                                   |
|------------+-----------------------------------------|
| 12.1XC     | Vulnerable; migrate to 12.2(31) or      |
|            | later                                   |
|------------+-----------------------------------------|
| 12.1XD     | Vulnerable; migrate to 12.2(31) or      |
|            | later                                   |
|------------+-----------------------------------------|
| 12.1XE     | Vulnerable; migrate to 12.1(26)E3 or    |
|            | later                                   |
|------------+-----------------------------------------|
| 12.1XF     | Vulnerable; migrate to 12.3(16) or      |
|            | later                                   |
|------------+-----------------------------------------|
| 12.1XG     | Vulnerable; migrate to 12.3(16) or      |
|            | later                                   |
|------------+-----------------------------------------|
| 12.1XH     | Vulnerable; migrate to 12.2(31) or      |
|            | later                                   |
|------------+-----------------------------------------|
| 12.1XI     | Vulnerable; migrate to 12.2(31) or      |
|            | later                                   |
|------------+-----------------------------------------|
| 12.1XJ     | Vulnerable; migrate to 12.3(16) or      |
|            | later                                   |
|------------+-----------------------------------------|
| 12.1XL     | Vulnerable; migrate to 12.3(16) or      |
|            | later                                   |
|------------+-----------------------------------------|
| 12.1XM     | Vulnerable; migrate to 12.3(16) or      |
|            | later                                   |
|------------+-----------------------------------------|
| 12.1XP     | Vulnerable; migrate to 12.3(16) or      |
|            | later                                   |
|------------+-----------------------------------------|
| 12.1XQ     | Vulnerable; migrate to 12.3(16) or      |
|            | later                                   |
|------------+-----------------------------------------|
| 12.1XR     | Vulnerable; migrate to 12.3(16) or      |
|            | later                                   |
|------------+-----------------------------------------|
| 12.1XS     | Vulnerable; migrate to 12.2(31) or      |
|            | later                                   |
|------------+-----------------------------------------|
| 12.1XT     | Vulnerable; migrate to 12.3(16) or      |
|            | later                                   |
|------------+-----------------------------------------|
| 12.1XU     | Vulnerable; migrate to 12.3(16) or      |
|            | later                                   |
|------------+-----------------------------------------|
| 12.1XV     | Vulnerable; migrate to 12.3(16) or      |
|            | later                                   |
|------------+-----------------------------------------|
| 12.1XW     | Vulnerable; migrate to 12.2(31) or      |
|            | later                                   |
|------------+-----------------------------------------|
| 12.1XX     | Vulnerable; migrate to 12.2(31) or      |
|            | later                                   |
|------------+-----------------------------------------|
| 12.1XY     | Vulnerable; migrate to 12.2(31) or      |
|            | later                                   |
|------------+-----------------------------------------|
| 12.1YA     | Vulnerable; migrate to 12.3(16) or      |
|            | later                                   |
|------------+-----------------------------------------|
| 12.1YB     | Vulnerable; migrate to 12.3(16) or      |
|            | later                                   |
|------------+-----------------------------------------|
| 12.1YC     | Vulnerable; migrate to 12.3(16) or      |
|            | later                                   |
|------------+-----------------------------------------|
| 12.1YD     | Vulnerable; migrate to 12.3(16) or      |
|            | later                                   |
|------------+-----------------------------------------|
| 12.1YE     | Vulnerable; migrate to 12.3(16) or      |
|            | later                                   |
|------------+-----------------------------------------|
| 12.1YF     | Vulnerable; migrate to 12.3(16) or      |
|            | later                                   |
|------------+-----------------------------------------|
| 12.1YH     | Vulnerable; migrate to 12.3(16) or      |
|            | later                                   |
|------------+-----------------------------------------|
| 12.1YI     | Vulnerable; migrate to 12.3(16) or      |
|            | later                                   |
|------------+-----------------------------------------|
| 12.1YJ     | Vulnerable; migrate to 12.1(22)EA4a,    |
|            | 12.1(22)EA5a, 12.1(22)EA6 or later      |
|------------+-----------------------------------------|
| Affected   |                    |                    |
| 12.2-Based | Rebuild            | Maintenance        |
| Release    |                    |                    |
|------------+--------------------+--------------------|
|            | 12.2(12m)          |                    |
|            |--------------------+--------------------|
|            | 12.2(17f)          |                    |
|            |--------------------+--------------------|
|            | 12.2(23f)          |                    |
|            |--------------------+--------------------|
| 12.2       | 12.2(26b)          |                    |
|            |--------------------+--------------------|
|            | 12.2(27b)          |                    |
|            |--------------------+--------------------|
|            | 12.2(28c)          |                    |
|            |--------------------+--------------------|
|            | 12.2(29a)          | 12.2(31)           |
|------------+-----------------------------------------|
| 12.2B      | Vulnerable; migrate to 12.3(14)T4 or    |
|            | later                                   |
|------------+-----------------------------------------|
| 12.2BC     | 12.2(15)BC2i       |                    |
|------------+-----------------------------------------|
| 12.2BX     | Vulnerable; migrate to 12.3(7)XI7,      |
|            | available 15-Nov-2005                   |
|------------+-----------------------------------------|
| 12.2BY     | Vulnerable; migrate to 12.3(14)T4 or    |
|            | later                                   |
|------------+-----------------------------------------|
| 12.2BZ     | Vulnerable; migrate to 12.3(7)XI7,      |
|            | available 15-Nov-2005                   |
|------------+-----------------------------------------|
| 12.2CX     | Vulnerable; migrate to 12.2(15)BC2i or  |
|            | later                                   |
|------------+-----------------------------------------|
| 12.2CY     | Vulnerable; migrate to 12.2(15)BC2i or  |
|            | later                                   |
|------------+-----------------------------------------|
|            | 12.2(15)CZ3,       |                    |
| 12.2CZ     | available          |                    |
|            | 3-Nov-2005         |                    |
|------------+--------------------+--------------------|
|            | 12.2(10)DA4        |                    |
| 12.2DA     |--------------------+--------------------|
|            | 12.2(12)DA9        |                    |
|------------+-----------------------------------------|
| 12.2DD     | Vulnerable; migrate to 12.3(14)T4 or    |
|            | later                                   |
|------------+-----------------------------------------|
| 12.2DX     | Vulnerable; migrate to 12.3(14)T4 or    |
|            | later                                   |
|------------+-----------------------------------------|
| 12.2EU     | 12.2(20)EU2        |                    |
|------------+--------------------+--------------------|
|            | 12.2(18)EW5        |                    |
| 12.2EW     |--------------------+--------------------|
|            | 12.2(20)EW3        |                    |
|------------+--------------------+--------------------|
|            | 12.2(20)EWA3       |                    |
|            |--------------------+--------------------|
| 12.2EWA    | 12.2(25)EWA3       |                    |
|            |--------------------+--------------------|
|            | 12.2(25)EWA4       |                    |
|------------+--------------------+--------------------|
|            |                    | 12.2(25)EX,        |
| 12.2EX     |                    | available          |
|            |                    | 03-Nov-2005        |
|------------+--------------------+--------------------|
| 12.2EY     | 12.2(25)EY3        | Migrate to 12.2    |
|            |                    | (25)SED            |
|------------+-----------------------------------------|
| 12.2EZ     | Vulnerable; migrate to 12.2(25)SEC2,    |
|            | 12.2(25)SED or later                    |
|------------+-----------------------------------------|
|            |                    | 12.2(25)FX,        |
| 12.2FX     |                    | available          |
|            |                    | 07-Nov-2005        |
|------------+--------------------+--------------------|
| 12.2FY     |                    | 12.2(25)FY         |
|------------+-----------------------------------------|
| 12.2JA     | Vulnerable; migrate to 12.3(7)JA1 or    |
|            | later                                   |
|------------+-----------------------------------------|
| 12.2JK     | 12.2(15)JK5        |                    |
|------------+--------------------+--------------------|
| 12.2MB     | 12.2(4)MB13c       |                    |
|------------+--------------------+--------------------|
| 12.2MC     | 12.2(15)MC2e       |                    |
|------------+--------------------+--------------------|
|            | 12.2(14)S15        |                    |
|            |--------------------+--------------------|
|            | 12.2(18)S10        |                    |
|            |--------------------+--------------------|
|            | 12.2(20)S9         |                    |
| 12.2S      |--------------------+--------------------|
|            | 12.2(25)S6         |                    |
|            |--------------------+--------------------|
|            | 12.2(30)S1,        |                    |
|            | available          |                    |
|            | 14-Nov-2005        |                    |
|------------+--------------------+--------------------|
| 12.2SBC    |                    | 12.2(27)SBC        |
|------------+--------------------+--------------------|
|            | 12.2(25)SEB4       | 12.2(25)SED        |
| 12.2SE     |--------------------+--------------------|
|            | 12.2(25)SEC2       |                    |
|------------+--------------------+--------------------|
| 12.2SG     |                    | 12.2(25)SG         |
|------------+--------------------+--------------------|
| 12.2SO     | 12.2(18)SO4        |                    |
|------------+-----------------------------------------|
| 12.2SU     | Vulnerable; migrate to 12.3(14)T4 or    |
|            | later                                   |
|------------+-----------------------------------------|
|            | 12.2(26)SV1        |                    |
|            |--------------------+--------------------|
| 12.2SV     | 12.2(27)SV1,       |                    |
|            | available          |                    |
|            | 15-Nov-2005        |                    |
|------------+--------------------+--------------------|
|            |                    | 12.2(25)SW4        |
| 12.2SW     |--------------------+--------------------|
|            |                    | 12.2(25)SW4a       |
|------------+-----------------------------------------|
| 12.2SX     | Vulnerable; migrate to 12.2(17d)SXB10   |
|            | or later                                |
|------------+-----------------------------------------|
| 12.2SXA    | Vulnerable; migrate to 12.2(17d)SXB10   |
|            | or later                                |
|------------+-----------------------------------------|
| 12.2SXB    | 12.2(17d)SXB10     |                    |
|------------+--------------------+--------------------|
| 12.2SXD    | 12.2(18)SXD6       |                    |
|------------+--------------------+--------------------|
| 12.2SXE    | 12.2(18)SXE3       |                    |
|------------+--------------------+--------------------|
| 12.2SXF    |                    | 12.2(18)SXF        |
|------------+-----------------------------------------|
| 12.2SY     | Vulnerable; migrate to 12.2(17d)SXB10   |
|            | or later                                |
|------------+-----------------------------------------|
| 12.2SZ     | Vulnerable; migrate to 12.2(25)S6 or    |
|            | later                                   |
|------------+-----------------------------------------|
| 12.2T      | 12.2(15)T17        |                    |
|------------+--------------------+--------------------|
| 12.2TPC    | 12.2(8)TPC10a,     |                    |
|            | available TBD      |                    |
|------------+-----------------------------------------|
| 12.2XA     | Vulnerable; migrate to 12.3(16) or      |
|            | later                                   |
|------------+-----------------------------------------|
| 12.2XB     | Vulnerable; migrate to 12.3(16) or      |
|            | later                                   |
|------------+-----------------------------------------|
| 12.2XC     | Vulnerable; migrate to 12.3(14)T4 or    |
|            | later                                   |
|------------+-----------------------------------------|
| 12.2XD     | Vulnerable; migrate to 12.3(16) or      |
|            | later                                   |
|------------+-----------------------------------------|
| 12.2XE     | Vulnerable; migrate to 12.3(16) or      |
|            | later                                   |
|------------+-----------------------------------------|
| 12.2XF     | Vulnerable; migrate to 12.2(15)BC2i or  |
|            | later                                   |
|------------+-----------------------------------------|
| 12.2XG     | Vulnerable; migrate to 12.3(16) or      |
|            | later                                   |
|------------+-----------------------------------------|
| 12.2XH     | Vulnerable; migrate to 12.3(16) or      |
|            | later                                   |
|------------+-----------------------------------------|
| 12.2XI     | Vulnerable; migrate to 12.3(16) or      |
|            | later                                   |
|------------+-----------------------------------------|
| 12.2XJ     | Vulnerable; migrate to 12.3(16) or      |
|            | later                                   |
|------------+-----------------------------------------|
| 12.2XK     | Vulnerable; migrate to 12.3(16) or      |
|            | later                                   |
|------------+-----------------------------------------|
| 12.2XL     | Vulnerable; migrate to 12.3(16) or      |
|            | later                                   |
|------------+-----------------------------------------|
| 12.2XM     | Vulnerable; migrate to 12.3(16) or      |
|            | later                                   |
|------------+-----------------------------------------|
| 12.2XN     | Vulnerable; migrate to 12.3(16) or      |
|            | later                                   |
|------------+-----------------------------------------|
| 12.2XQ     | Vulnerable; migrate to 12.3(16) or      |
|            | later                                   |
|------------+-----------------------------------------|
|            | 12.2(2)XR and 12.2(4)XR vulnerable,     |
|            | migrate to 12.3(16) or later            |
| 12.2XR     |-----------------------------------------|
|            | 12.2(15)XR vulnerable; migrate to 12.3  |
|            | (7)JA1                                  |
|------------+-----------------------------------------|
| 12.2XS     | Vulnerable; migrate to 12.3(16) or      |
|            | later                                   |
|------------+-----------------------------------------|
| 12.2XT     | Vulnerable; migrate to 12.3(16) or      |
|            | later                                   |
|------------+-----------------------------------------|
| 12.2XU     | Vulnerable; migrate to 12.3(16) or      |
|            | later                                   |
|------------+-----------------------------------------|
| 12.2XV     | Vulnerable; migrate to 12.3(16) or      |
|            | later                                   |
|------------+-----------------------------------------|
| 12.2XW     | Vulnerable; migrate to 12.3(16) or      |
|            | later                                   |
|------------+-----------------------------------------|
| 12.2YA     | 12.2(4)YA11,       |                    |
|            | available TBD      |                    |
|------------+-----------------------------------------|
| 12.2YB     | Vulnerable; migrate to 12.3(16) or      |
|            | later                                   |
|------------+-----------------------------------------|
| 12.2YC     | Vulnerable; migrate to 12.3(16) or      |
|            | later                                   |
|------------+-----------------------------------------|
| 12.2YD     | Vulnerable; migrate to 12.3(14)T4 or    |
|            | later                                   |
|------------+-----------------------------------------|
| 12.2YE     | Vulnerable; migrate to 12.2(25)S6 or    |
|            | later                                   |
|------------+-----------------------------------------|
| 12.2YF     | Vulnerable; migrate to 12.3(16) or      |
|            | later                                   |
|------------+-----------------------------------------|
| 12.2YG     | Vulnerable; migrate to 12.3(16) or      |
|            | later                                   |
|------------+-----------------------------------------|
| 12.2YH     | Vulnerable; migrate to 12.3(16) or      |
|            | later                                   |
|------------+-----------------------------------------|
| 12.2YJ     | Vulnerable; migrate to 12.3(16) or      |
|            | later                                   |
|------------+-----------------------------------------|
| 12.2YK     | Vulnerable; migrate to 12.3(14)T4 or    |
|            | later                                   |
|------------+-----------------------------------------|
| 12.2YL     | Vulnerable; migrate to 12.3(14)T4 or    |
|            | later                                   |
|------------+-----------------------------------------|
| 12.2YM     | Vulnerable; migrate to 12.3(14)T4 or    |
|            | later                                   |
|------------+-----------------------------------------|
| 12.2YN     | Vulnerable; migrate to 12.3(14)T4 or    |
|            | later                                   |
|------------+-----------------------------------------|
| 12.2YO     | Vulnerable; migrate to 12.2(17d)SXB10   |
|            | or later                                |
|------------+-----------------------------------------|
| 12.2YP     | Vulnerable; migrate to 12.3(16) or      |
|            | later                                   |
|------------+-----------------------------------------|
| 12.2YQ     | Vulnerable; migrate to 12.3(14)T4 or    |
|            | later                                   |
|------------+-----------------------------------------|
| 12.2YR     | Vulnerable; migrate to 12.3(14)T4 or    |
|            | later                                   |
|------------+-----------------------------------------|
| 12.2YS     |                    | 12.2(15)YS         |
|------------+-----------------------------------------|
| 12.2YT     | Vulnerable; migrate to 12.3(16) or      |
|            | later                                   |
|------------+-----------------------------------------|
| 12.2YU     | Vulnerable; migrate to 12.3(14)T4 or    |
|            | later                                   |
|------------+-----------------------------------------|
| 12.2YV     | Vulnerable; migrate to 12.3(14)T4 or    |
|            | later                                   |
|------------+-----------------------------------------|
| 12.2YW     | Vulnerable; migrate to 12.3(14)T4 or    |
|            | later                                   |
|------------+-----------------------------------------|
| 12.2YX     | Vulnerable; migrate to 12.3(14)T4 or    |
|            | later                                   |
|------------+-----------------------------------------|
| 12.2YY     | Vulnerable; migrate to 12.3(14)T4 or    |
|            | later                                   |
|------------+-----------------------------------------|
| 12.2YZ     | Vulnerable; migrate to 12.2(25)S6 or    |
|            | later                                   |
|------------+-----------------------------------------|
| 12.2ZA     | Vulnerable; migrate to 12.2(17d)SXB10   |
|            | or later                                |
|------------+-----------------------------------------|
| 12.2ZB     | Vulnerable; migrate to 12.3(14)T4 or    |
|            | later                                   |
|------------+-----------------------------------------|
| 12.2ZC     | Vulnerable; migrate to 12.3(14)T4 or    |
|            | later                                   |
|------------+-----------------------------------------|
| 12.2ZD     | 12.2(13)ZD4        |                    |
|------------+-----------------------------------------|
| 12.2ZE     | Vulnerable; migrate to 12.3(16) or      |
|            | later                                   |
|------------+-----------------------------------------|
| 12.2ZF     | Vulnerable; migrate to 12.3(14)T4 or    |
|            | later                                   |
|------------+-----------------------------------------|
|            | Vulnerable; migrate to 12.3(8)YG3 or    |
| 12.2ZG     | later for SOHO9x migrate to 12.3(2)XA5  |
|            | or later for c83x                       |
|------------+-----------------------------------------|
| 12.2ZH     | 12.2(13)ZH8,       |                    |
|            | available TBD      |                    |
|------------+-----------------------------------------|
| 12.2ZJ     | Vulnerable; migrate to 12.3(14)T4 or    |
|            | later                                   |
|------------+-----------------------------------------|
|            | Vulnerable; migrate to 12.3(4)XK4 or    |
| 12.2ZL     | later for c17xx migrate to 12.4(3a) or  |
|            | later for c3200 migrate to 12.3(7)XR6   |
|            | or later for ICS7750                    |
|------------+-----------------------------------------|
| 12.2ZN     | Vulnerable; migrate to 12.3(14)T4 or    |
|            | later                                   |
|------------+-----------------------------------------|
| 12.2ZP     | Vulnerable; migrate to 12.3(14)T4 or    |
|            | later                                   |
|------------+-----------------------------------------|
| Affected   |                    |                    |
| 12.3-Based | Rebuild            | Maintenance        |
| Release    |                    |                    |
|------------+--------------------+--------------------|
|            | 12.3(3i)           |                    |
|            |--------------------+--------------------|
|            | 12.3(5f)           |                    |
|            |--------------------+--------------------|
|            | 12.3(6f)           |                    |
|            |--------------------+--------------------|
|            | 12.3(9e)           |                    |
| 12.3       |--------------------+--------------------|
|            | 12.3(10e)          |                    |
|            |--------------------+--------------------|
|            | 12.3(12e)          |                    |
|            |--------------------+--------------------|
|            | 12.3(13b)          |                    |
|            |--------------------+--------------------|
|            | 12.3(15b)          | 12.3(16)           |
|------------+-----------------------------------------|
| 12.3B      | Vulnerable; migrate to 12.3(14)T4 or    |
|            | later                                   |
|------------+-----------------------------------------|
|            | 12.3(9a)BC7        |                    |
| 12.3BC     |--------------------+--------------------|
|            | 12.3(13a)BC1       |                    |
|------------+-----------------------------------------|
| 12.3BW     | Vulnerable; migrate to 12.3(14)T4 or    |
|            | later                                   |
|------------+-----------------------------------------|
|            | 12.3(2)JA5         |                    |
|            |--------------------+--------------------|
| 12.3JA     | 12.3(4)JA1         |                    |
|            |--------------------+--------------------|
|            | 12.3(7)JA1         |                    |
|------------+--------------------+--------------------|
| 12.3JK     | 12.3(2)JK1         |                    |
|------------+--------------------+--------------------|
| 12.3JX     | 12.3(7)JX          |                    |
|------------+--------------------+--------------------|
|            | 12.3(7)T12         |                    |
|            |--------------------+--------------------|
|            | 12.3(8)T11         |                    |
| 12.3T      |--------------------+--------------------|
|            | 12.3(11)T8         |                    |
|            |--------------------+--------------------|
|            | 12.3(14)T4         |                    |
|------------+--------------------+--------------------|
| 12.3TPC    | 12.3(4)TPC11a      |                    |
|------------+--------------------+--------------------|
| 12.3XA     | 12.3(2)XA5,        |                    |
|            | available TBD      |                    |
|------------+-----------------------------------------|
| 12.3XB     | Vulnerable; migrate to 12.3(14)T4 or    |
|            | later                                   |
|------------+-----------------------------------------|
| 12.3XC     | 12.3(2)XC4         |                    |
|------------+-----------------------------------------|
| 12.3XD     | Vulnerable; migrate to 12.3(14)T4 or    |
|            | later                                   |
|------------+-----------------------------------------|
| 12.3XE     | 12.3(4)XE4,        |                    |
|            | available TBD      |                    |
|------------+-----------------------------------------|
| 12.3XF     | Vulnerable; migrate to 12.3(14)T4 or    |
|            | later                                   |
|------------+-----------------------------------------|
| 12.3XG     | 12.3(4)XG5         |                    |
|------------+-----------------------------------------|
| 12.3XH     | Vulnerable; migrate to 12.3(14)T4 or    |
|            | later                                   |
|------------+-----------------------------------------|
|            | 12.3(7)XI7,        |                    |
| 12.3XI     | available          |                    |
|            | 15-Nov-2005        |                    |
|------------+-----------------------------------------|
| 12.3XJ     | Vulnerable; migrate to 12.3(11)YF4 or   |
|            | later                                   |
|------------+-----------------------------------------|
| 12.3XK     | 12.3(4)XK4         |                    |
|------------+-----------------------------------------|
| 12.3XM     | Vulnerable; migrate to 12.3(14)T4 or    |
|            | later                                   |
|------------+-----------------------------------------|
| 12.3XQ     | Vulnerable; migrate to 12.4(3a) or      |
|            | later                                   |
|------------+-----------------------------------------|
| 12.3XR     | 12.3(7)XR6         |                    |
|------------+-----------------------------------------|
| 12.3XS     | Vulnerable; migrate to 12.4(3a) or      |
|            | later                                   |
|------------+-----------------------------------------|
| 12.3XU     | Vulnerable; migrate to 12.4(2)T1 or     |
|            | later                                   |
|------------+-----------------------------------------|
| 12.3XW     | Vulnerable; migrate to 12.3(11)YF4 or   |
|            | later                                   |
|------------+-----------------------------------------|
| 12.3XX     | Vulnerable; migrate to 12.4(3a) or      |
|            | later                                   |
|------------+-----------------------------------------|
| 12.3XY     | Vulnerable; migrate to 12.3(14)T4 or    |
|            | later                                   |
|------------+-----------------------------------------|
|            | Vulnerable; migrate to 12.4(3a) or      |
| 12.3YA     | later for C828; migrate to 12.3(8)YG3   |
|            | or later for SOHO9x, C83x               |
|------------+-----------------------------------------|
| 12.3YD     | Vulnerable; migrate to 12.4(2)T1 or     |
|            | later                                   |
|------------+-----------------------------------------|
| 12.3YF     | 12.3(11)YF4        |                    |
|------------+--------------------+--------------------|
| 12.3YG     | 12.3(8)YG3         |                    |
|------------+-----------------------------------------|
| 12.3YH     | Vulnerable; migrate to 12.3(8)YI3 or    |
|            | later                                   |
|------------+-----------------------------------------|
| 12.3YI     | 12.3(8)YI3         |                    |
|------------+--------------------+--------------------|
| 12.3YJ     | 12.3(14)YQ3        |                    |
|------------+--------------------+--------------------|
| 12.3YK     | 12.3(11)YK2        |                    |
|------------+--------------------+--------------------|
| 12.3YQ     | 12.3(14)YQ3        |                    |
|------------+--------------------+--------------------|
| 12.3YS     | 12.3(11)YS1        |                    |
|------------+--------------------+--------------------|
| 12.3YT     | 12.3(14)YT1        |                    |
|------------+--------------------+--------------------|
| 12.3YU     | 12.3(14)YU1        |                    |
|------------+--------------------+--------------------|
| Affected   |                    |                    |
| 12.4-Based | Rebuild            | Maintenance        |
| Release    |                    |                    |
|------------+--------------------+--------------------|
|            | 12.4(1b)           |                    |
| 12.4       |--------------------+--------------------|
|            | 12.4(3a)           |                    |
|------------+--------------------+--------------------|
| 12.4MR     |                    | 12.4(2)MR1         |
|------------+--------------------+--------------------|
| 12.4T      | 12.4(2)T1          |                    |
|------------+--------------------+--------------------|
| 12.4XA     |                    | 12.4(2)XA          |
|------------+--------------------+--------------------|
|            |                    | 12.4(2)XB,         |
| 12.4XB     |                    | available          |
|            |                    | 18-Nov-2005        |
+------------------------------------------------------+

Obtaining Fixed Software
========================

Customers with Service Contracts
+-------------------------------

Customers with contracts should obtain upgraded software through their
regular update channels. For most customers, this means that upgrades
should be obtained through the Software Center on Cisco's worldwide
website at http://www.cisco.com.

Customers using Third-party Support Organizations
+------------------------------------------------

Customers whose Cisco products are provided or maintained through prior
or existing agreement with third-party support organizations such as
Cisco Partners, authorized resellers, or service providers should
contact that support organization for assistance with the upgrade,
which should be free of charge.

Customers without Service Contracts
+----------------------------------

Customers who purchase direct from Cisco but who do not hold a Cisco
service contract and customers who purchase through third-party vendors
but are unsuccessful at obtaining fixed software through their point of
sale should get their upgrades by contacting the Cisco Technical
Assistance Center (TAC). TAC contacts are as follows.

  * +1 800 553 2447 (toll free from within North America)
  * +1 408 526 7209 (toll call from anywhere in the world)
  * e-mail: tac@cisco.com

Please have your product serial number available and give the URL of
this notice as evidence of your entitlement to a free upgrade. Free
upgrades for non-contract customers must be requested through the TAC.

Please do not contact either "psirt@cisco.com" or
"security-alert@cisco.com" for software upgrades.

See http://www.cisco.com/warp/public/687/Directory/DirTAC.shtml for
additional TAC contact information, including special localized
telephone numbers and instructions and e-mail addresses for use in
various languages.

Customers may only install and expect support for the feature sets they
have purchased. By installing, downloading, accessing or otherwise
using such software upgrades, customers agree to be bound by the terms
of Cisco's software license terms found at 
http://www.cisco.com/public/sw-license-agreement.html, or as otherwise 
set forth at Cisco.com Downloads at 
http://www.cisco.com/public/sw-center/sw-usingswc.shtml.

Workarounds
===========

There are no workarounds or configuration changes that will implement
counter-measures equivalent to the increased integrity checks on system
timers that have been introduced. In order to reduce the potential for
system timer-related arbitrary code execution, an IOS upgrade is
necessary.

Successful exploitation requires an appropriate attack vector such as
the vulnerability described in 
http://www.cisco.com/warp/publics/707/cisco-sa-20050729-ipv6.shtml. 
Vulnerability specific workarounds and mitigation steps may help to 
minimize the threat to the device by removing or minimizing the 
available attack vectors, but the device could still be vulnerable 
through any other attack vectors in which a software fix or mitigation 
has not been implemented.

Exploitation and Public Announcements
=====================================

The Cisco PSIRT is not aware of malicious use of the vulnerability
described in this advisory. Exploit code exists for this vulnerability.
It was used in a demonstration by Mike Lynn on July 27, 2005 at the
Black Hat USA 2005 security conference where a heap overflow via an
IPv6 attack vector achieved remote code execution. The IPv6 attack
vector was addressed separately in a Cisco security advisory released
on July 29, 2005.

Status of This Notice: FINAL
============================

THIS ADVISORY IS PROVIDED ON AN "AS IS" BASIS AND DOES NOT IMPLY ANY
KIND OF GUARANTEE OR WARRANTY, INCLUDING THE WARRANTY OF
MERCHANTABILITY. YOUR USE OF THE INFORMATION ON THE ADVISORY OR
MATERIALS LINKED FROM THE ADVISORY IS AT YOUR OWN RISK. CISCO RESERVES
THE RIGHT TO CHANGE OR UPDATE THIS NOTICE AT ANY TIME.

A stand-alone copy or paraphrase of the text of this security advisory
that omits the distribution URL in the following section is an
uncontrolled copy, and may lack important information or contain
factual errors.

Distribution
============

This advisory is posted on Cisco's worldwide website at 
http://www.cisco.com/warp/public/707/cisco-sa-20051102-timers.shtml.

In addition to worldwide web posting, a text version of this notice is
clear-signed with the Cisco PSIRT PGP key and is posted to the
following e-mail and Usenet news recipients.

  * cust-security-announce@cisco.com
  * first-teams@first.org (includes CERT/CC)
  * bugtraq@securityfocus.com
  * vulnwatch@vulnwatch.org
  * cisco@spot.colorado.edu
  * cisco-nsp@puck.nether.net
  * full-disclosure@lists.grok.org.uk
  * comp.dcom.sys.cisco@newsgate.cisco.com

Future updates of this advisory, if any, will be placed on Cisco's
worldwide website, but may or may not be actively announced on mailing
lists or newsgroups. Users concerned about this problem are encouraged
to check the above URL for any updates.

Revision History
================

+----------------------------------------------------+
|              |            |                        |
| Revision 1.0 | 2-Nov-2005 | Initial public release |
|              |            |                        |
+----------------------------------------------------+

Cisco Security Procedures
=========================

Complete information on reporting security vulnerabilities in Cisco
products, obtaining assistance with security incidents, and registering
to receive security information from Cisco, is available on Cisco's
worldwide website at 
http://www.cisco.com/en/US/products/products_security_vulnerability_policy.html.
This includes instructions for press inquiries regarding Cisco security 
notices. All Cisco security advisories are available at 
http://www.cisco.com/go/psirt.

- -----------------------------------------------------------------------

All contents are Copyright 1992-2005 Cisco Systems, Inc. All rights
reserved. 

- -----------------------------------------------------------------------

Updated: Nov 02, 2005                                Document ID: 68064

- -----------------------------------------------------------------------
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