AUSCERT External Security Bulletin Redistribution

                  ESB-2001.362 -- Cisco Security Advisory
            CBOS Web-based Configuration Utility Vulnerability
                              24 August 2001


        AusCERT Security Bulletin Summary

Product:                Cisco 600 series routers
Vendor:                 Cisco Systems
Operating System:       Cisco Broadband Operating System (CBOS)
Impact:                 Denial of Service
Access Required:        Remote

Ref:                    ESB-2001.302

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Cisco Security Advisory: CBOS Web-based Configuration Utility Vulnerability

Revision 1.0

For Public Release 2001 August 23 20:00 (UTC -800)



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://www.cisco.com/warp/public/707/cisco-cbos-webserver-pub.shtml.

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.

No other releases of CBOS software are affected by this vulnerability. No
other Cisco products are affected by this vulnerability.

These defects will be fixed in the following CBOS releases: 2.4.2b and



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.


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.

Software Versions and Fixes

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.

|    Major     |   Description      | Availability of Repaired Releases |
|   Release    |   or Platform      |                                   |   
|              |                    |     General Availability (GA)     |   
| All releases |   All platforms    |               2.4.3               |
|              |                    |            2001-AUG-23            |

Obtaining Fixed Software

Cisco is providing software patches and upgrades to supported products to
remedy the vulnerability for all affected Cisco customers.

Customers with contracts should obtain upgraded software through their
regular update channels. Customers whose Cisco products are provided or
maintained through prior or existing agreements with third-party support
organizations such as Cisco Partners, authorized resellers, or service
providers should contact that support organization for  upgrade assistance
and instructions.  For most Cisco customers, upgrades are available through
the Software Center on Cisco's Worldwide Web site at http://www.cisco.com/.

Customers without contracts can obtain the software by contacting the Cisco
Technical Assistance Center (TAC). TAC contacts are as follows:

   * (800) 553 2447 (toll-free from within North America)
   * +1 408 526 7209 (toll call from anywhere in the world)
   * E-mail: tac@cisco.com

See http://www.cisco.com/warp/public/687/Directory/DirTAC.shtml for
additional TAC contact information, including instructions and e-mail
addresses for use in various languages.

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.


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

Exploitation and Public Announcements

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

   * http://www.cert.org/advisories/CA-2001-19.html
   * http://www.eeye.com/html/Research/Advisories/AD20010618.html

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 information has been checked to the
best of our ability. Should there be a significant change in the facts,
Cisco may update this notice.


This notice will be posted on Cisco's Worldwide Web site at
http://www.cisco.com/warp/public/707/cisco-cbos-webserver-pub.shtml. 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:

   * cust-security-announce@cisco.com
   * bugtraq@securityfocus.com
   * firewalls@lists.gnac.com
   * first-teams@first.org (includes CERT/CC)
   * cisco@spot.colorado.edu
   * cisco-nsp@puck.nether.net
   * nanog@nanog.org
   * incidents@securityfocus.com
   * comp.dcom.sys.cisco
   * Various internal Cisco mailing lists

Future updates of this notice, 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 URL given above for any updates.

Revision History

| Revision  | 2001-Aug-23 20:00 (UTC -800)  | Initial public release        |
| 1.0       |                               |                               |

Cisco Product Security Incident 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
Web site at
http://www.cisco.com/warp/public/707/sec_incident_response.shtml. This
includes instructions for press inquiries regarding Cisco security notices.


This notice is Copyright 2001 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, including
all date and version information.


Version: PGP 6.5.2


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