Advisory ID: cisco-sa-20010823-cbos-webserver
For Public Release 2001 August 23 04:00 UTC (GMT)
Multiple vulnerabilities have been identified and fixed in the Cisco Broadband Operating System (CBOS), an operating system for the Cisco 600 family of routers. Any router in the Cisco 600 series family can be made unresponsive by a large amount of HTTP traffic accessing the web-based configuration utility on the router; additionally the web-based configuration utility is enabled by default. This is documented in Cisco Bug IDs CSCdv06084, CSCdv06088, CSCdv06089, and CSCdv06098.
This advisory is available at http://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20010823-cbos-webserver.
This section provides details on affected products.
The affected models are: 627, 633, 673, 675, 675E, 677, 677i and 678.
These models are vulnerable if they run any of the following, or earlier, CBOS releases: 2.0.1, 2.1.0, 2.1.0a, 2.2.0, 2.2.1, 2.2.1a, 2.3, 2.3.2, 2.3.5, 2.3.7, 2.3.8, 2.3.9, 2.4.1, 2.4.2, and 2.4.2ap.
These defects will be fixed in the following CBOS releases: 2.4.2b and 2.4.3.
No other releases of CBOS software are affected by this vulnerability. No other Cisco products are affected by this vulnerability.
When the Cisco 600 series router is accessed via telnet via multiple connections, the router will fail to pass traffic, and may become unresponsive to configuration attempts, requiring a reboot to recover to normal operation.
When the Cisco 600 series router is accessed via HTTP via multiple connections, the router will fail to pass traffic, and may become unresponsive to configuration attempts, requiring a reboot to recover to normal operation.
The web-based configuration utility in Cisco Broadband Operating System (CBOS) binds itself to a TCP port (port 80 unless configured for another port) even when web-based configuration services are disabled. This leaves the Cisco 600 series router vulnerable to CSCdv06088 even when the affected service is apparently disabled.
The web-based utility is now disabled by default, allowing customers to choose to enable this configuration option.
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 combination of each of these issues causes the Cisco 600 series router to be vulnerable to a Denial-of-service attack. None of these defects results in a failure of confidentiality of information stored on the unit. None of these defects allow hostile code to be loaded onto the Cisco 600 series router.
The following table summarizes the CBOS software releases affected by the vulnerabilities described in this notice and scheduled dates on which the earliest corresponding fixed releases will be available.
Description or Platform
Availability of Repaired Releases
General Availability (GA)
There is no specific workaround for each of these vulnerabilities; however, a workaround exists which has proven a reasonable defense for the CodeRed Worm attack. It is advisable to disable web management on port 80, by setting the web management port to some number greater than 1024, with the following command, replacing the text "number_greater-than_1024" with an actual number.
set web port number_greater-than_1024
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.
This issue is being exploited actively and has been discussed in numerous public announcements and messages. The most common occurrence of exploitation has been via the spread of the CodeRed Worm. References include:
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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 advisory will be posted on Cisco's worldwide website at http://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20010823-cbos-webserver.
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 the Cisco Security Advisories page at http://www.cisco.com/go/psirt/, 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.
Updated "Obtaining Fixed Software" section
Initial public release.