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Home » Hacking News » Cisco Security Advisory: Cisco CatOS Embedded HTTP Server Buffer Overflow

Cisco Security Advisory: Cisco CatOS Embedded HTTP Server Buffer Overflow

by Nikola Strahija on October 16th, 2002 Cisco Catalyst switches running specific versions of Cisco CatOS software are vulnerable to a buffer overflow in an embedded HTTP server. Only CatOS versions from 5.4 up to and including 7.3 which contain a "cv" in the image name are affected. If the HTTP server is enabled a buffer overflow can be remotely exploited which will cause the switch to fail and reload. The vulnerability can be exploited repeatedly and result in a denial of service. Workarounds are available that limit the ability to exploit the vulnerability. This advisory will be published at

Affected Products

This vulnerability is only present in Cisco Catalyst switches running Cisco
CatOS software versions 5.4 through 7.3 that contain an embedded HTTP server to
support CiscoView network management software. The affected software images
contain "cv" in the image name as seen here: cat6000-supcv.5-5-16.bin.


If the HTTP server is enabled on a Cisco Catalyst switch running an affected
CiscoView image, an overly long HTTP query can be received by the embedded HTTP
server that will cause a buffer overflow and result in a software reset of the
switch. Once the switch has recovered and has resumed normal processing it is
vulnerable again. It remains vulnerable until the HTTP server is disabled, HTTP
queries to the switch management port are blocked, or the switch's software has
been upgraded to a fixed version.

The HTTP server is disabled by default. It is typically enabled to allow web
based management of the switch using CiscoView. Only a small subset of CatOS
images contain this embedded HTTP server.

This vulnerability is documented as DDTS:
CSCdy26428 - CatOS crash with web server enabled in http_get_token.


The exploitation of this issue can result in a software forced reset of this
device. Repeated exploitation may lead to a denial of service until the
workaround for this vulnerability has been implemented or a fixed version of
software has been loaded onto the device.

Software Versions and Fixes

All versions of CatOS software with the embedded HTTP server are vulnerable
prior to the fixed versions listed below. Each row of the table 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 and the anticipated date of availability for each are listed in
the Rebuild, Interim, and Maintenance columns. A device running any release in
the given train that is earlier than the release in a specific column (less
than the earliest fixed release) is known to be vulnerable, and it should be
upgraded at least to the indicated release or a later version (greater than the
earliest fixed release label).

When selecting a release, keep in mind the following definitions:


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


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, and interim images should be
upgraded to the next available maintenance release as soon as possible.
Interim releases are not available via manufacturing, and usually they are
not available for customer download from CCO without prior arrangement with
the Cisco Technical Assistance Center (TAC).

| Release | Interim | Maintenance |
| 5.x | 5.5(16.2) | 5.5(17) |
| 6.x | 6.3(8.3) | 6.3(9) |
| 7.3 | not yet fixed | not yet fixed |
| 7.4 | 7.4(0.63) | 7.4(1) |

Obtaining Fixed Software

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

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 obtaining the free software upgrade

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)
* email: [email protected]

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

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 "[email protected]" or "[email protected]"
for software upgrades.


The HTTP server can be disabled on the on the Cisco switch.

This example shows how to disable the HTTP server:

Console (enable) set ip http server disable
HTTP server disabled.

The default setting for the HTTP server is disabled.

You may also choose to block access to port 80 for your Cisco switch. This can
be done with any device with traffic filtering capabilties.

Exploitation and Public Announcements

The Cisco PSIRT is not aware of any public announcements or malicious use of
the vulnerabilities described in this advisory. This issue has been reported to
Cisco by multiple customers.

Status of This Notice: FINAL

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


This notice will be posted on Cisco's worldwide website at
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:

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

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

Revision History

|Revision No. 1.0 |2002-October-16 17:00 UTC |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 This includes
instructions for press inquiries regarding Cisco security notices. All Cisco
Security Advisories are available at

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

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

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

All contents are Copyright © 1992--2002 Cisco Systems, Inc. All rights

Version: PGP 6.5.2


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