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             AUSCERT External Security Bulletin Redistribution

                         ESB-2006.0178 -- [Cisco]
            Cisco response to multiple PIX DoS vulnerabilities
                               9 March 2006


        AusCERT Security Bulletin Summary

Product:           Cisco PIX 7.0
                   Cisco PIX 6.3
Publisher:         Cisco Systems
Operating System:  Cisco
Impact:            Denial of Service
Access:            Remote/Unauthenticated

Ref:               ESB-2005.0935

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Cisco Response

This is Cisco PSIRT's response to the statements made by Arhont Ltd.-
Information Security in their messages: 
"[Full-disclosure] Cisco PIX embryonic state machine TTL(n-1) DoS"
"[Full-disclosure] Cisco PIX embryonic state machine 1b data DoS"
both posted on March 7, 2006.

The original emails are available at:  

These issues have the same root cause that was documented in Arhont
Ltd.- Information Security's message: 
"[Full-disclosure] Cisco PIX TCP Connection Prevention",
posted on November 22, 2005 at: 

As detailed in our reply also dated November 22, 2005, this issue is
being tracked by two Cisco Bug ID's:

  * CSCsc14915 -- PIX 6.3 Spoofed TCP SYN packets can block
    legitimate TCP connections
    This Bug ID tracks the issue for PIX software version 6.3 and
    older. This DDTS is resolved and available in PIX software
    version 6.3(5.106). There are workarounds available to mitigate
    the issue.

  * CSCsc16014 -- PIX 7.0 Spoofed TCP SYN packets can block
    legitimate TCP connections
    This Bug ID tracks the issue for PIX/ASA software version 7.0.
    This DDTS is resolved and available in PIX/ASA software versions
    7.0(4.005) and 7.1(1). Additional mitigations and workarounds
    exist to limit or eliminate the issue.

Our November 22, 2005 reply is available at:

We would like to thank Arhont Ltd.- Information Security for ensuring
that these issues were previously addressed as well.

We greatly appreciate the opportunity to work with researchers on
security vulnerabilities, and welcome the opportunity to review and
assist in product reports.

Additional Information

There have been updates to the information available for these two
Bug ID's since November 22, 2005. The updated Release Note Enclosures
are available at:

CSCsc14915 -- PIX 6.3 Spoofed TCP SYN packets can block legitimate
TCP connections

(registered customers only: http://tools.cisco.com/RPF/register/register.do)

CSCsc16014 -- PIX 7.0 Spoofed TCP SYN packets can block legitimate
TCP connections

(registered customers only: http://tools.cisco.com/RPF/register/register.do)

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 
This includes instructions for press inquiries regarding Cisco 
security notices. All Cisco security advisories are available at 

Version: GnuPG v1.4.0 (SunOS)


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