BugTraq
Cisco Security Advisory: Cisco IOS Malformed BGP packet causes reload Jun 16 2004 03:00PM
Cisco Systems Product Security Incident Response Team (psirt cisco com)
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Cisco Security Advisory: Cisco IOS Malformed BGP Packet Causes Reload

Revision 1.0
============

Last Updated June 16 15:00 UTC (GMT)

For Public Release 2004 June 16 15:00 UTC (GMT)

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Please provide your feedback on this document.

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Contents

Summary
Affected Products
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

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Summary
=======

A Cisco device running IOS and enabled for the Border Gateway Protocol (BGP) is
vulnerable to a Denial of Service (DOS) attack from a malformed BGP packet. The
BGP protocol is not enabled by default, and must be configured in order to
accept traffic from an explicitly defined peer. Unless the malicious traffic
appears to be sourced from a configured, trusted peer, it would be difficult to
inject a malformed packet.

Cisco has made free software available to address this problem.

This advisory is available at
http://www.cisco.com/warp/public/707/cisco-sa-20040616-bgp.shtml.

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

Vulnerable Products

This issue affects all Cisco devices running any unfixed version of Cisco IOS
code and configured for BGP routing.

A router which is running the BGP process will have a line in the config
defining the AS number, which can be seen by issuing the command show
running-config:

router bgp <AS number>

This vulnerability is present in any unfixed version of IOS, from the beginning
of support for the BGP protocol, including versions 9.x, 10.x, 11.x and 12.x.

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 12.0(3)
with an installed image name of C2500-IS-L:

Cisco Internetwork Operating System Software IOS (TM)

2500 Software (C2500-IS-L), Version 12.0(3), RELEASE SOFTWARE

The release train label is "12.0."

The next example shows a product running IOS release 12.0(2a)T1 with an image
name of C2600-JS-MZ:

Cisco Internetwork Operating System Software IOS (tm)
C2600 Software (C2600-JS-MZ), Version 12.0(2a)T1, RELEASE SOFTWARE (fc1)

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

Products Confirmed Not Vulnerable

Products confirmed not to be vulnerable include devices which cannot
participate in BGP or cannot be configured for BGP.

Details
=======

The Border Gateway Protocol (BGP) is a routing protocol defined by RFC 1771,
and designed to manage IP routing in large networks. An affected Cisco device
running a vulnerable version of Cisco IOS software and enabling the BGP
protocol will reload when a malformed BGP packet is received. BGP runs over
TCP, a reliable transport protocol which requires a valid three way handshake
before any further messages will be accepted. The Cisco IOS implementation of
BGP requires the explicit definition of a neighbor before a connection can be
established, and traffic must appear to come from that neighbor. These
implementation details make it very difficult to send a BGP packet to a Cisco
IOS device from an unauthorized source.

A Cisco device receiving an invalid BGP packet will reset and may take several
minutes to become fully functional. This vulnerability may be exploited
repeatedly resulting in an extended DOS attack. This issue is documented in bug
IDs CSCdu53656 and CSCea28131.

Impact
======

Successful exploitation of this vulnerability results in a reload of the
device. Repeated exploitation could result in a sustained DoS attack.

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

Note: Many of the releases in this table were fixed prior to the release of
other IOS advisories. Read the table carefully to determine if your IOS release
contains these fixes. Most fixed releases for the TCP and SNMP advisories such
as http://www.cisco.com/warp/public/707/cisco-sa-20040420-snmp.shtml and
http://www.cisco.com/warp/public/707/cisco-sa-20040420-tcp-ios.shtml
contained the fixes for this BGP advisory.

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," "Interim," 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). When selecting a
release, keep in mind the following definitions:

Maintenance

Most heavily tested, stable, and highly recommended release of a release train
in any given row of the table.

Rebuild

Constructed from the previous maintenance or major release in the same train,
it contains the fix for a specific defect. Although it receives less testing,
it contains only the minimal changes necessary to repair the vulnerability.

Interim

Built at regular intervals between maintenance releases and receives less
testing. Interims should be selected only if there is no other suitable release
that addresses the vulnerability. Interim images should be upgraded to the next
available maintenance release as soon as possible. Interim releases are not
available through manufacturing, and usually they are not available for
customer download from Cisco.com without prior arrangement with the Cisco TAC.

In all cases, customers should exercise caution to confirm that the devices to
be upgraded contain sufficient memory and that current hardware and software
configurations will continue to be supported properly by the new software
release. If the information is not clear, contact the Cisco TAC for assistance
as shown in the Obtaining Fixed Software section below.

More information on Cisco IOS software release names and abbreviations is
available at http://www.cisco.com/warp/public/620/1.html.

The fixes will be available at the Software Center located at
http://www.cisco.com/tacpage/sw-center/.

For software installation and upgrade procedures, see
http://www.cisco.com/warp/public/130/upgrade_index.shtml.

For a current view of all posted and repaired images for Cisco IOS, please
check the listing available to registered Cisco.com users at:
http://www.cisco.com/tacpage/sw-center/sw-ios.shtml.

+------------------------------------------------+
| Major | Availability of Repaired Releases |
| Release | * |
|------------+-----------------------------------|
| Affected | | Interim | |
| 11.1-Based | Rebuild | ** | Maintenance |
| Release | | | |
|------------+-----------------------------------|
| 11.1 | Migrate to 11.2 or later |
|------------+-----------------------------------|
| 11.1AA | Migrate to 11.2P or later |
|------------+-----------------------------------|
| 11.1CA | Migrate to 12.0 or later |
|------------+-----------------------------------|
| 11.1CC | Migrate to 12.0 or later |
|------------+-----------------------------------|
| Affected | | Interim | |
| 11.2-Based | Rebuild | ** | Maintenance |
| Release | | | |
|------------+-----------+---------+-------------|
| 11.2 | 11.2(26g) | | |
|------------+-----------+---------+-------------|
| 11.2P | 11.2(26) | | |
| | P7 | | |
|------------+-----------------------------------|
| 11.2SA | Not Vulnerable |
|------------+-----------------------------------|
| Affected | | Interim | |
| 11.3-Based | Rebuild | ** | Maintenance |
| Release | | | |
|------------+-----------+---------+-------------|
| 11.3 | 11.3(11f) | | |
|------------+-----------+---------+-------------|
| 11.3T | 11.3(11b) | | |
| | T5 | | |
|------------+-----------+---------+-------------|
| Affected | | Interim | |
| 12.0-Based | Rebuild | ** | Maintenance |
| Release | | | |
|------------+-----------+---------+-------------|
| 12.0 | | | 12.0(27) |
|------------+-----------------------------------|
| 12.0DA | Migrate to 12.2DA or later |
|------------+-----------------------------------|
| | 12.0(21) | | |
| | S7 | | |
| |-----------+---------+-------------|
| | 12.0(22) | | |
| | S2e | | |
| |-----------+---------+-------------|
| | 12.0(22) | | |
| | S3c | | |
| |-----------+---------+-------------|
| | 12.0(22) | | |
| | S4a | | |
| |-----------+---------+-------------|
| 12.0S | 12.0(22) | | |
| | S5 | | |
| |-----------+---------+-------------|
| | 12.0(23) | | |
| | S3 | | |
| |-----------+---------+-------------|
| | 12.0(24) | | |
| | S2 | | |
| |-----------+---------+-------------|
| | 12.0(25) | | |
| | S1 | | |
| |-----------+---------+-------------|
| | | | 12.0(26)S |
|------------+-----------------------------------|
| 12.0SL | Migrate to 12.0(23)S3 or later |
|------------+-----------------------------------|
| | 12.0(17) | | |
| | ST10 | | |
| | Available | | |
| | upon | | |
| 12.0ST | request | | |
| |-----------+---------+-------------|
| | 12.0(21) | | |
| | ST7 | | |
| |-----------------------------------|
| | Migrate to 12.0(26)S2 or later |
|------------+-----------------------------------|
| 12.0SV | | | 12.0(27)SV |
|------------+-----------+---------+-------------|
| 12.0SX | 12.0(25) | | |
| | SX | | |
|------------+-----------+---------+-------------|
| | 12.0(23) | | |
| | SZ3 | | |
|12.0SZ |-----------+---------+-------------|
| | | | 12.0(26)SZ |
| |-----------------------------------|
| | Migrate to 12.0(26)S2 or later |
|------------+-----------------------------------|
| 12.0T | Migrate to 12.1 or later |
|------------+-----------------------------------|
| | 12.0(16) | | |
| | W5(21c) | | |
| |-----------+---------+-------------|
| | 12.0(25) | | |
| | W5(27b) | | |
|12.0W5 |-----------+---------+-------------|
| | 12.0(26) | | |
| | W5(28a) | | |
| |-----------+---------+-------------|
| | 12.0(27) | | |
| | W5(29) | | |
|------------+-----------------------------------|
| 12.0WC | Not Vulnerable |
|------------+-----------------------------------|
| 12.0WX | Migrate to 12.0W5 or later |
|------------+-----------------------------------|
| 12.0XA | Migrate to 12.1 latest or later |
|------------+-----------------------------------|
| 12.0XC | Migrate to 12.1 latest or later |
|------------+-----------------------------------|
| 12.0XD | Migrate to 12.1 latest or later |
|------------+-----------------------------------|
| 12.0XE | Migrate to 12.1E latest or later |
|------------+-----------------------------------|
| 12.0XG | Migrate to 12.1 latest or later |
|------------+-----------------------------------|
| 12.0XH | Migrate to 12.1 latest or later |
|------------+-----------------------------------|
| 12.0XI | Migrate to 12.1 latest or later |
|------------+-----------------------------------|
| 12.0XJ | Migrate to 12.1 latest or later |
|------------+-----------------------------------|
| 12.0XK | Migrate to 12.1T latest or later |
|------------+-----------------------------------|
| 12.0XL | Migrate to 12.2 latest or later |
|------------+-----------------------------------|
| 12.0XN | Migrate to 12.1 latest or later |
|------------+-----------------------------------|
| 12.0XP | Not Vulnerable |
|------------+-----------------------------------|
| 12.0XR | Migrate to 12.2 latest or later |
|------------+-----------------------------------|
| 12.0XS | Migrate to 12.1E latest or later |
|------------+-----------------------------------|
| 12.0XU | Not Vulnerable |
|------------+-----------------------------------|
| Affected | | Interim | |
| 12.1-Based | Rebuild | ** | Maintenance |
| Release | | | |
|------------+-----------+---------+-------------|
| 12.1 | | | 12.1(20) |
|------------+-----------------------------------|
| 12.1AA | Migrate to 12.2 latest or later |
|------------+-----------------------------------|
| | Not Vulnerable |
|12.1AX |-----------------------------------|
| | 12.1AY | Not Vulnerable |
|------------+-----------+-----------------------|
| 12.1AZ | | | 12.1(14)AZ |
|------------+-----------------------------------|
| 12.1DA | Migrate to 12.2DA or later |
|------------+-----------------------------------|
| 12.1DB | Migrate to 12.2B or later |
|------------+-----------------------------------|
| | 12.1(6) | | |
| | E12.0 | | |
| |-----------+---------+-------------|
| | 12.1(8b) | | |
| | E14 | | |
| |-----------+---------+-------------|
| | 12.1(11b) | | |
| | E12.0 | | |
| |-----------+---------+-------------|
| | 12.1(12c) | | |
| 12.1E | E7 | | |
| |-----------+---------+-------------|
| | 12.1(13) | | |
| | E6 | | |
| |-----------+---------+-------------|
| | 12.1(14) | | |
| | E4 | | |
| |-----------+---------+-------------|
| | 12.1(19)E | | |
| |-----------+---------+-------------|
| | | | 12.1(20)E |
|------------+-----------+---------+-------------|
| 12.1EA | 12.1(14) | | |
| | EA1 | | |
|------------+-----------+---------+-------------|
| 12.1EB | 12.1(14) | | |
| | EB1 | | |
|------------+-----------+---------+-------------|
| 12.1EC | | | 12.1(19)EC |
|------------+-----------+---------+-------------|
| 12.1EO | | | 12.1(19)EO |
|------------+-----------+---------+-------------|
| 12.1EV | 12.1(12c) | | |
| | EV2 | | |
|------------+-----------+---------+-------------|
| 12.1EW | | | 12.1(19)EW |
|------------+-----------------------------------|
| 12.1EX | Migrate to 12.1(14)E4 or later |
|------------+-----------------------------------|
| 12.1EY | Migrate to 12.1(14)E4 or later |
|------------+-----------------------------------|
| 12.1T | 12.1(5) | | |
| | T19 | | |
|------------+-----------------------------------|
| 12.1XA | Migrate to 12.1(5)T19 or later |
|------------+-----------------------------------|
| 12.1XB | Migrate to 12.1(5)T19 or later |
|------------+-----------------------------------|
| 12.1XC | Migrate to 12.1(5)T19 or later |
|------------+-----------------------------------|
| 12.1XD | Migrate to 12.2 or later |
|------------+-----------------------------------|
| 12.1XE | Migrate to 12.1E latest or later |
|------------+-----------------------------------|
| 12.1XF | Migrate to 12.2(4)T6 or later |
|------------+-----------------------------------|
| 12.1XG | Migrate to 12.2(4)T6 or later |
|------------+-----------------------------------|
| 12.1XH | Migrate to 12.2 or later |
|------------+-----------------------------------|
| 12.1XI | Migrate to 12.2 latest or later |
|------------+-----------------------------------|
| 12.1XJ | Migrate to 12.2(4)T6 or later |
|------------+-----------------------------------|
| 12.1XL | Migrate to 12.2T latest or later |
|------------+-----------------------------------|
| 12.1XM | Migrate to 12.2T latest or later |
|------------+-----------------------------------|
| 12.1XP | Migrate to 12.2(4)T6 or later |
|------------+-----------------------------------|
| 12.1XQ | Migrate to 12.2T latest or later |
|------------+-----------------------------------|
| 12.1XR | Migrate to 12.2T latest or later |
|------------+-----------------------------------|
| 12.1XT | Migrate to 12.2(4)T6 or later |
|------------+-----------------------------------|
| 12.1XU | Migrate to 12.2T latest or later |
|------------+-----------------------------------|
| 12.1XV | Migrate to 12.2XB or later |
|------------+-----------------------------------|
| 12.1XY | Migrate to 12.2XB or later |
|------------+-----------------------------------|
| 12.1YA | Migrate to 12.2(8)T10 or later |
|------------+-----------------------------------|
| 12.1YB | Migrate to 12.2(4)T6 or later |
|------------+-----------------------------------|
| 12.1YC | Migrate to 12.2(8)T10 or later |
|------------+-----------------------------------|
| 12.1YD | Migrate to 12.2(8)T10 or later |
|------------+-----------------------------------|
| 12.1YH | Migrate to 12.2(13)T5 or later |
|------------+-----------------------------------|
| 12.1YJ | Not Vulnerable |
|------------+-----------------------------------|
| Affected | | Interim | |
| 12.2-Based | Rebuild | ** | Maintenance |
| Release | | | |
|------------+-----------+---------+-------------|
| | 12.2(10d) | | |
| |-----------+---------+-------------|
| | 12.2(12e) | | |
| |-----------+---------+-------------|
| | 12.2(12h) | | |
| 12.2 | M1 | | |
| |-----------+---------+-------------|
| | 12.2(13c) | | |
| |-----------+---------+-------------|
| | 12.2(16a) | | |
| |-----------+---------+-------------|
| | | | 12.2(17) |
|------------+-----------+---------+-------------|
| 12.2B | 12.2(15) | | |
| | B1 | | |
|------------+-----------+---------+-------------|
| 12.2BC | 12.2(15) | | |
| | BC1 | | |
|------------+-----------------------------------|
| 12.2BW | Migrate to 12.2(15)T12 or later |
|------------+-----------------------------------|
| 12.2BX | | | 12.2(16)BX |
|------------+-----------------------------------|
| 12.2BY | Migrate to 12.2(15)B1 or later |
|------------+-----------------------------------|
| 12.2BZ | Migrate to 12.2(16)BX or later |
|------------+-----------------------------------|
| 12.2CX | | | 12.2(15)CX |
|------------+-----------+---------+-------------|
| 12.2DA | 12.2(12) | | |
| | DA6 | | |
|------------+-----------------------------------|
| 12.2DD | Migrate to 12.2(15)B1 or later |
|------------+-----------------------------------|
| 12.2DX | Migrate to 12.2(15)B1 or later |
|------------+-----------------------------------|
| 12.2EW | | | 12.2(18)EW |
|------------+-----------+---------+-------------|
| 12.2JA | | | 12.2(13)JA |
|------------+-----------+---------+-------------|
| | 12.2(14) | | |
| 12.2S | S2 | | |
| |-----------+---------+-------------|
| | | | 12.2(18)S |
|------------+-----------+---------+-------------|
| 12.2SE | | | 12.2(18)SE |
|------------+-----------+---------+-------------|
| 12.2SU | | | 12.2(14)SU |
|------------+-----------+---------+-------------|
| 12.2SV | | | 12.2(18)SV |
|------------+-----------+---------+-------------|
| 12.2SW | | | 12.2(18)SW |
|------------+-----------+---------+-------------|
| 12.2SX | 12.2(14) | | |
| | SX2 | | |
|------------+-----------+---------+-------------|
| 12.2SXA | 12.2(17b) | | |
| | SXA | | |
|------------+-----------+---------+-------------|
| 12.2SXB | 12.2(17d) | | |
| | SXB | | |
|------------+-----------+---------+-------------|
| 12.2SY | | | 12.2(14)SY |
|------------+-----------+---------+-------------|
| 12.2SZ | 12.2(14) | | |
| | SZ2 | | |
|------------+-----------+---------+-------------|
| | 12.2(4)T6 | | |
| |-----------+---------+-------------|
| | 12.2(8) | | |
| | T10 | | |
| |-----------+---------+-------------|
| | 12.2(11) | | |
| 12.2T | T9 | | |
| |-----------+---------+-------------|
| | 12.2(13) | | |
| | T5 | | |
| |-----------+---------+-------------|
| | 12.2(15) | | |
| | T4 | | |
|------------+-----------------------------------|
| 12.2XA | Migrate to 12.2(11)T9 or later |
|------------+-----------------------------------|
| 12.2XB | 12.2(2) | | |
| | XB16 | | |
|------------+-----------------------------------|
| 12.2XD | Migrate to 12.2(8)T10 or later |
|------------+-----------------------------------|
| 12.2XE | Migrate to 12.2(8)T10 or later |
|------------+-----------------------------------|
| 12.2XG | Migrate to 12.2(8)T10 or later |
|------------+-----------------------------------|
| 12.2XH | Migrate to 12.2(11)T9 or later |
|------------+-----------------------------------|
| 12.2XI | Migrate to 12.2(11)T9 or later |
|------------+-----------------------------------|
| 12.2XJ | Migrate to 12.2(11)T9 or later |
|------------+-----------------------------------|
| 12.2XK | Migrate to 12.2(11)T9 or later |
|------------+-----------------------------------|
| 12.2XL | Migrate to 12.2(15)T4 or later |
|------------+-----------------------------------|
| 12.2XM | Migrate to 12.2(15)T4 or later |
|------------+-----------------------------------|
| 12.2XN | Migrate to 12.2(11)T9 or later |
|------------+-----------------------------------|
| 12.2XQ | Migrate to 12.2(11)T9 or later |
|------------+-----------------------------------|
| 12.2XS | Migrate to 12.2(11)T9 or later |
|------------+-----------------------------------|
| 12.2XT | Migrate to 12.2(11)T9 or later |
|------------+-----------------------------------|
| 12.2XU | Migrate to 12.2(15)T12 or later |
|------------+-----------------------------------|
| 12.2XW | Migrate to 12.2(11)T9 or later |
|------------+-----------------------------------|
| 12.2YA | Migrate to 12.2(15)T4 or later |
|------------+-----------------------------------|
| 12.2YB | Migrate to 12.2(15)T4 or later |
|------------+-----------------------------------|
| 12.2YC | Migrate to 12.2(11)T11 or later |
|------------+-----------------------------------|
| 12.2YD | Migrate to 12.2(8)YY or later |
|------------+-----------------------------------|
| 12.2YE | Migrate to 12.2S or later |
|------------+-----------------------------------|
| 12.2YF | Migrate to 12.2(15)T4 or later |
|------------+-----------------------------------|
| 12.2YG | Migrate to 12.2(13)T5 or later |
|------------+-----------------------------------|
| 12.2YH | Migrate to 12.2(15)T4 or later |
|------------+-----------------------------------|
| 12.2YJ | Migrate to 12.2(15)T4 or later |
|------------+-----------------------------------|
| 12.2YL | Migrate to 12.3(2)T or later |
|------------+-----------------------------------|
| 12.2YM | Migrate to 12.3(2)T or later |
|------------+-----------------------------------|
| 12.2YN | Migrate to 12.3(2)T or later |
|------------+-----------------------------------|
| 12.2YO | Migrate to 12.2(14)SY or later |
|------------+-----------------------------------|
| 12.2YP | 12.2(11) | | |
| | YP1 | | |
|------------+-----------------------------------|
| 12.2YQ | Migrate to 12.3(4)T or later |
|------------+-----------------------------------|
| 12.2YR | Migrate to 12.3(4)T or later |
|------------+-----------------------------------|
| 12.2YS | Migrate to 12.3T or later |
|------------+-----------------------------------|
| 12.2YT | Migrate to 12.2(15)T4 or later |
|------------+-----------------------------------|
| 12.2YU | Migrate to 12.3(4)T or later |
|------------+-----------------------------------|
| 12.2YV | Migrate to 12.3(4)T or later |
|------------+-----------------------------------|
| 12.2YW | Migrate to 12.3(2)T or later |
|------------+-----------------------------------|
| 12.2YX | Migrate to 12.2(14)SU or later |
|------------+-----------------------------------|
| 12.2YY | 12.2(8) | | |
| | YY3 | | |
|------------+-----------------------------------|
| 12.2YZ | Migrate to 12.2(14)SZ or later |
|------------+-----------------------------------|
| 12.2ZA | 12.2(14) | | |
| | ZA2 | | |
|------------+-----------------------------------|
| 12.2ZB | Migrate to 12.3T or later |
|------------+-----------------------------------|
| 12.2ZC | Migrate to 12.3T or later |
|------------+-----------------------------------|
| 12.2ZE | Migrate to 12.3 or later |
|------------+-----------------------------------|
| 12.2ZF | Migrate to 12.3(4)T or later |
|------------+-----------------------------------|
| 12.2ZG | Migrate to 12.3(4)T or later |
|------------+-----------------------------------|
| 12.2ZH | Migrate to 12.3(4)T or later |
|------------+-----------------------------------|
| 12.2ZI | Migrate to 12.2(18)S or later |
|------------+-----------------------------------|
| 12.2ZK | | | 12.2(15)ZK |
|------------+-----------+---------+-------------|
| 12.2ZL | | | 12.2(15)ZL |
|------------+-----------------------------------|
| 12.2ZN | Migrate to 12.3(2)T or later |
|------------+-----------------------------------|
| 12.2ZO | | | 12.2(15)ZO |
|------------+-----------+---------+-------------|
| 12.2ZP | | | 12.2(13)ZP |
|------------+-----------+---------+-------------|
| Affected | | Interim | |
| 12.3-Based | Rebuild | ** | Maintenance |
| Release | | | |
|------------+-----------------------------------|
| 12.3 | Not Vulnerable |
|------------+-----------------------------------|
| 12.3T | Not Vulnerable |
+------------------------------------------------+

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/tacpage/sw-center.

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 (at) cisco (dot) com [email concealed]

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 (at) cisco (dot) com [email concealed]" or "security-alert (at) cisco (dot) com [email concealed]"
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
===========

The effectiveness of any workaround is dependent on specific customer
situations such as product mix, network topology, traffic behavior, and
organizational mission. Due to the variety of affected products and releases,
customers should consult with their service provider or support organization to
ensure any applied workaround is the most appropriate for use in the intended
network before it is deployed.

For additional information regarding BGP security risk assessment, mitigation
techniques, and deployment best practices, please consult ftp://
ftp-eng.cisco.com/cons/isp/security/BGP-Risk-Assesment-v.pdf.

BGP MD5

Under normal circumstances, due to inherent security factors in the TCP
protocol such as sequence number checks, it is difficult but possible to forge
an appropriate packet to exploit this problem. Configuring your Cisco IOS
device for BGP MD5 authentication is a valid workaround to protect the
vulnerable device.

This can be configured as shown in the following example:

router(config)# router bgp
router(config-router)# neighbor <IP_address> password <enter_your_secret_here>

It is necessary to configure the same shared MD5 secret on both peers and at
the same time. Failure to do so will break the existing BGP session and the new
session will not get established until the exact same secret is configured on
both devices. For a detailed discussion on how to configure BGP, refer to the
following document:

http://www.cisco.com/en/US/products/sw/iosswrel/ps1828/products_configur
ation_guide_chapter09186a00800ca571.html

Once the secret is configured, it is prudent to change it periodically. The
exact period must fit within your company security policy but it should not be
longer than a few months. When changing the secret, again it must be done at
the same time on both devices. Failure to do so will break your existing BGP
session. The exception is if your Cisco IOS software release contains the
integrated CSCdx23494 fix on both sides of the connection. With this fix,
the BGP session will not be terminated when the MD5 secret is changed only
on one side. The BGP updates, however, will not be processed until either
the same secret is configured on both devices or the secret is removed from
both devices.

Infrastructure Access Control Lists

Although it is often difficult to block traffic transiting your network, it is
possible to identify traffic which should never be allowed to target your
infrastructure devices and block that traffic at the border of your network.
Infrastructure ACLs are considered a network security best practice and should
be considered as a long-term addition to good network security as well as a
workaround for this specific vulnerability. The white paper entitled
"Protecting Your Core: Infrastructure Protection Access Control Lists" presents
guidelines and recommended deployment techniques for infrastructure protection
ACLs:

http://www.cisco.com/warp/public/707/iacl.html

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

The research which led to this vulnerability being discovered was announced in
a public announcement at NANOG in June 2003. The Cisco PSIRT team is not aware
of any malicious use of the vulnerabilities described in this advisory. We were
made aware of this issue through internal testing as well as notification from
a research team at the University of California at Santa Barbara.

The Cisco PSIRT is not aware of any malicious use of the vulnerability
described in this advisory.

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

This Advisory is provided on an "as is" basis and does not imply any kind of
guarantee or warranty of any kind. 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 anytime.

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

This advisory will be posted on Cisco's worldwide website at
http://www.cisco.com/warp/public/707/cisco-sa-20040616-bgp.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 (at) cisco (dot) com [email concealed]
* first-teams (at) first (dot) org [email concealed] (includes CERT/CC)
* bugtraq (at) securityfocus (dot) com [email concealed]
* vulnwatch (at) wulnwatch (dot) org [email concealed]
* cisco (at) spot.colorado (dot) edu [email concealed]
* cisco-nsp (at) puck.nether (dot) net [email concealed]
* full-disclosure (at) lists.netsys (dot) com [email concealed]
* comp.dcom.sys.cisco (at) newsgate.cisco (dot) com [email concealed]

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 | 16-June-2004 | Initial Public |
| 1.0 | | 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/warp/public/707/sec_incident_response.shtml. 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 © 1992-2004 Cisco Systems, Inc. All rights reserved.

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