[NEWS] Cisco CatOS Embedded HTTP Server Buffer Overflow

From: support@securiteam.com
Date: 10/16/02 

From: support@securiteam.com
To: list@securiteam.com
Date: 16 Oct 2002 23:53:15 +0200

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  Cisco CatOS Embedded HTTP Server Buffer Overflow
------------------------------------------------------------------------

SUMMARY

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.

DETAILS

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.

Details:
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 contains this embedded HTTP server.

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

Impact:
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:

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

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, 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).

For a table listing all available patches and fixes see:
 
<http://www.cisco.com/warp/public/707/catos-http-overflow-vuln.shtml#Software> http://www.cisco.com/warp/public/707/catos-http-overflow-vuln.shtml#Software

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 <http://www.cisco.com/kobayashi/sw-center/sw-lan.shtml>
http://www.cisco.com/kobayashi/sw-center/sw-lan.shtml.

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(s).

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: tac@cisco.com.

See <http://www.cisco.com/warp/public/687/Directory/DirTAC.shtml>
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.

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@cisco.com" or
"security-alert@cisco.com" for software upgrades.

Workarounds:
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 capabilities.

ADDITIONAL INFORMATION

The information has been provided by <mailto:psirt@cisco.com> Cisco
Systems Product Security Incident Response Team.

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