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             AUSCERT External Security Bulletin Redistribution

                    ESB-2008.0986 -- [Appliance][Cisco]
         Cisco Response to Outpost24 TCP State Table Manipulation
                     Denial of Service Vulnerabilities
                              20 October 2008

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        AusCERT Security Bulletin Summary
        ---------------------------------

Publisher:            Cisco Systems
Operating System:     Cisco
                      Network Appliance
Impact:               Denial of Service
Access:               Remote/Unauthenticated

Comment: This is Cisco's response to a reported vulnerability in TCP which
         allows a remote unauthenticated attacker to cause a Denial of
         Service on the TCP connection queue.

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Cisco Security Response: Cisco Response to Outpost24 TCP State Table
                         Manipulation Denial of Service
                         Vulnerabilities

Revision 1.0

For Public Release 2008 October 17 1600 UTC (GMT)

+---------------------------------------------------------------------

Contents
========

    Cisco Response
    Additional Information
    Revision History
    Cisco Security Procedures

Cisco Response
==============

This is Cisco's response to research presented by Robert E. Lee and
Jack Louis of Outpost24 who have announced several denial of service
(DoS) vulnerabilities that involve the manipulation of TCP state
table information. These vulnerabilities have been discussed on
numerous websites and blogs, including a presentation delivered by
Lee and Louis at the T2 conference in Helsinki, Finland on October
17, 2008.

Cisco PSIRT is aware of the vulnerabilities and is actively
investigating what impact these vulnerabilities may have on Cisco
products. PSIRT will disclose any security vulnerabilities discovered
in compliance with Cisco's security vulnerability policy:

http://www.cisco.com/en/US/products/products_security_vulnerability_policy.html

PSIRT is working with Outpost24 and the Finnish Computer Emergency
Response Team (CERT-FI) as part of the industry response to these
vulnerabilities. An announcement from CERT-FI is available at the
following link:

https://www.cert.fi/haavoittuvuudet/2008/tcp-vulnerabilities.html

This security response is posted at:

http://www.cisco.com/warp/public/707/cisco-sr-20081017-tcp.shtml

Additional Information
======================

Cisco PSIRT research indicates an attacker must complete a TCP
three-way handshake to a device to successfully exploit the DoS
vulnerabilities. This requirement makes spoofing the source of an
attack more challenging. The TCP vulnerabilities that Outpost24
announced are an extension of well-known weaknesses in the TCP
protocol.

It is possible to mitigate the risk of these vulnerabilities by
allowing only trusted sources to access TCP-based services. This
mitigation is particularly important for critical infrastructure
devices. PSIRT recommends the implementation of infrastructure access
control lists (IACLs) and control plane policing (CoPP) to protect
core network functionality. For more information, reference the IACL
documentation at the following links:

http://www.cisco.com/en/US/tech/tk648/tk361/technologies_white_paper09186a00801a1a55.shtml

http://www.cisco.com/en/US/tech/tk648/tk361/technologies_tech_note09186a0080120f48.shtml#limitaccess

Information on CoPP can be found at the following links:

http://www.cisco.com/web/about/security/intelligence/coppwp_gs.html

http://www.cisco.com/en/US/tech/tk648/tk361/technologies_tech_note09186a0080120f48.shtml

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

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

+---------------------------------------+
| Revision |                 | Initial  |
| 1.0      | 2008-October-17 | 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
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