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Home » Hacking News » Cisco Security Advisory: Cisco PIX Multiple Vulnerabilities

Cisco Security Advisory: Cisco PIX Multiple Vulnerabilities

by Nikola Strahija on November 22nd, 2002 The Cisco PIX Firewall provides robust, enterprise-class security services including stateful inspection firewalling, standards-based IP Security (IPsec) Virtual Private Networking (VPN), intrusion protection and much more in cost-effective, easy to deploy solutions.

Two vulnerabilities have been resolved for the PIX firewall for which
fixes are available. These vulnerabilities are documented as Cisco bug ID
CSCdv83490 and CSCdx35823. There are no workarounds available to mitigate
the effects of these vulnerabilities.

This advisory will be posted at

Affected Products

All PIX Firewall units running the vulnerable releases and using the
specific features are affected by these vulnerabilities.

No other Cisco products are currently known to be affected by these

| DDTs-Description |Affected Release |
|CSCdv83490-While processing |6.0.3 and earlier|
|initial contact notify messages|6.1.3 and earlier|
|the PIX does not delete | |
|duplicate Internet Security | |
|Authentication Key Management | |
|Protocol Security Associations | |
|(ISAKMP SAs) with the peer. | |
|CSCdx35823-Buffer overflow |5.2.8 and earlier|
|while doing HTTP traffic |6.0.3 and earlier|
|authentication using Terminal |6.1.3 and earlier|
|Access Controller Access |6.2.1 and earlier|
|Control System Plus (TACACS+) | |
|or Remote Authentication | |
|Dial-In User Service (RADIUS). | |

To determine your software revision, type show version at the command line


When a user establishes a VPN session upon successful peer and
user authentication, the PIX creates an ISAKMP SA associating the
user and his IP address.

If an attacker is now able to block the logged-in user's
connection and establish a connection to the PIX using the same IP
address as that of the user, he will be able to establish a VPN
session with the PIX, using only peer authentication, provided he
already has access to the peer authentication key also known as
the group pre-shared key (PSK) or group password key.

A user starting a connection via FTP, Telnet, or over the World
Wide Web (HTTP) is prompted for their user name and password. If
the user name and password are verified by the designated TACACS+
or RADIUS authentication server, the PIX Firewall unit will allow
further traffic between the authentication server and the
connection to interact independently through the PIX Firewall
unit's "cut-through proxy" feature.

The PIX may crash and reload due to a buffer overflow
vulnerability while processing HTTP traffic requests for
authentication using TACACS+ or RADIUS.

The Internetworking Terms and Acronyms online guide can be found at The Cisco
Systems Terms and Acronyms online guide can be found at

These vulnerabilities are documented in the Bug Toolkit as Bug IDs
CSCdv83490 and CSCdx35823, and can be viewed after 2002 November 21 at
1600 UTC. To access this tool, you must be a registered user and you must
be logged in.


| DDTs-Description | Impact |
|CSCdv83490-While |This vulnerability can |
|processing initial |be exploited to |
|contact notify messages |initiate a |
|the PIX does not delete |Man-In-The-Middle |
|duplicate ISAKMP SA's |attack for VPN sessions|
|with the peer. |to the PIX. |
|CSCdx35823 - Buffer |This vulnerability can |
|overflow while doing HTTP|be exploited to |
|traffic authentication |initiate a |
|using TACACS+ or RADIUS. |Denial-of-Service |
| |attack. |

Software Versions and Fixes

| DDTs-Description |Fixed Releases|
|CSCdv83490-While processing |6.0.4 and |
|initial contact notify messages |later |
|the PIX does not delete duplicate |6.1.4 and |
|ISAKMP SAs with the peer. |later |
| |6.2.1 and |
| |later |
|CSCdx35823-Buffer overflow while |5.2.9 and |
|doing HTTP traffic authentication |later |
|using TACACS+ or RADIUS. |6.0.4 and |
| |later |
| |6.1.4 and |
| |later |
| |6.2.2 and |
| |later |

The procedure to upgrade to the fixed software version is detailed at

Obtaining Fixed Software

Cisco is offering free software upgrades to address these vulnerabilities
for all affected customers. Customers may only install and expect support
for the feature sets they have purchased.

Customers with service contracts should contact their regular update
channels to obtain the free software upgrade identified via this advisory.
For most customers with service contracts, this means that upgrades should
be obtained through the Software Center on Cisco's worldwide website at To access the software,
download URL, you must be
a registered user and you must be logged in.

Customers whose Cisco products are provided or maintained through a 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 obtaining the free software

Customers who purchased directly 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 obtain fixed software by contacting the Cisco Technical
Assistance Center (TAC) using the contact information listed below. In
these cases, customers are entitled to obtain an upgrade to a later
version of the same release or as indicated by the applicable corrected
software version in the Software Versions and Fixes section (noted above).

Cisco 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: [email protected]

See for
additional TAC contact information, including special localized telephone
numbers and instructions and e-mail addresses for use in various

Please have your product serial number available and give the URL of this
advisory as evidence of your entitlement to a free upgrade.

Please do not contact either "[email protected]" or
"[email protected]" for software upgrades.


There are no workarounds for these vulnerabilities. The Cisco PSIRT
recommends that affected users upgrade to a fixed software version of

Exploitation and Public Announcements

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

These vulnerabilities were reported to PSIRT by Cisco engineering and

Status of This Advisory: FINAL

This is a final advisory. Although Cisco cannot guarantee the accuracy of
all statements in this advisory, all of the facts have been checked to the
best of our ability. Cisco does not anticipate issuing updated versions of
this advisory unless there is some material change in the facts. Should
there be a significant change in the facts, Cisco may update this

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


This advisory will be posted on Cisco's worldwide website at

In addition to worldwide website posting, a text version of this advisory
is clear-signed with the Cisco PSIRT PGP key having the fingerprint FEB1
1B89 A64B 60BB 4770 D1CE 93D2 FF06 F236 759C and is posted to the
following e-mail and Usenet news recipients:

* [email protected]
* [email protected]
* [email protected]
* [email protected] (includes CERT/CC)
* [email protected]
* [email protected]
* Various internal Cisco mailing lists

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 | 2002-Nov-20 | Initial public release |
| 1.0 | | |

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
advisories. All Cisco security advisories are available at


This advisory is Copyright 2002 by Cisco Systems, Inc. This advisory may
be redistributed freely after the release date given at the top of the
text, provided that redistributed copies are complete and unmodified,
including all date and version information.

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