Advisory ID: cisco-sa-20021016-catos-http-overflow
For Public Release 2002 October 16 16:00 UTC (GMT)
Vulnerability Scoring Details
Software Versions and Fixes
Obtaining Fixed Software
Exploitation and Public Announcements
Status of this Notice: Final
Cisco Security Procedures
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 http://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20021016-catos-http-overflow.
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: cat6000-supcv.5-5-16.bin.
No other Cisco products are currently known to be affected by these vulnerabilities.
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.
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 http://www.cisco.com/public/sw-license-agreement.html, or as otherwise set forth at Cisco.com Downloads at http://www.cisco.com/public/sw-center/sw-usingswc.shtml.
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 http://www.cisco.com.
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 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)
- e-mail: email@example.com
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.
Refer to 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.
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.
THIS DOCUMENT IS PROVIDED ON AN "AS IS" BASIS AND DOES NOT IMPLY ANY KIND OF GUARANTEE OR WARRANTY, INCLUDING THE WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR USE. YOUR USE OF THE INFORMATION ON THE DOCUMENT OR MATERIALS LINKED FROM THE DOCUMENT IS AT YOUR OWN RISK. CISCO RESERVES THE RIGHT TO CHANGE OR UPDATE THIS DOCUMENT AT ANY TIME.
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 http://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20021016-catos-http-overflow. 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:
- firstname.lastname@example.org (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.
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 http://www.cisco.com/en/US/products/products_security_vulnerability_policy.html. This includes instructions for press inquiries regarding Cisco security notices. All Cisco security advisories are available at http://www.cisco.com/go/psirt.