Advisory ID: cisco-sa-20021016-catos-http-overflow
For Public Release 2002 October 16 16:00 UTC (GMT)
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
This section provides details on 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:
No other Cisco products are currently known to be affected by these
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.
Cisco has provided scores for the vulnerabilities in this advisory based on the Common Vulnerability Scoring System (CVSS). The CVSS scoring in this Security Advisory is done in accordance with CVSS version 2.0.
CVSS is a standards-based scoring method that conveys vulnerability severity and helps determine urgency and priority of response.
Cisco has provided a base and temporal score. Customers can then compute environmental scores to assist in determining the impact of the vulnerability in individual networks.
Cisco has provided an FAQ to answer additional questions regarding CVSS at
Cisco has also provided a CVSS calculator to help compute the environmental impact for individual networks at
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.
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).
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.
Cisco has made free software available to address this vulnerability
for affected customers. Prior to deploying software, customers should consult
their maintenance provider or check the software for feature set compatibility
and known issues specific to their environment.
Customers may only install and expect support for the feature sets they
have purchased. By installing, downloading, accessing or otherwise using such
software upgrades, customers agree to be bound by the terms of Cisco's software
license terms found at
or as otherwise set forth at Cisco.com Downloads at
Do not contact either "email@example.com" or "firstname.lastname@example.org"
for software upgrades.
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 guidance and assistance with the appropriate course of
action in regards to this advisory.
The effectiveness of any workaround or fix is dependent on specific
customer situations such as product mix, network topology, traffic behavior,
and organizational mission. Due to the variety of affected products and
releases, customers should consult with their service provider or support
organization to ensure any applied workaround or fix is the most appropriate
for use in the intended network before it is deployed.
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 in obtaining fixed software through their point of sale should obtain software patches and bug fixes 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)
Have your product serial number available and provide the URL of this notice as evidence of entitlement to a software patch or bug fix. Customers without service contracts should request a software patch or bug fix through the TAC.
for additional TAC contact information, including special localized telephone
numbers and instructions and e-mail addresses for use in various
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.
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A stand-alone copy or Paraphrase of the text of this document that omits the distribution URL in the following section is an uncontrolled copy, and may lack important information or contain factual errors.
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@example.com (includes CERT/CC)
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 Number 1.1
Updated the "Software Versions and Fixes" section to remove
software version 7.3, which was listed as "not yet fixed."
Revision Number 1.0
Initial public release.