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Cisco Security Advisory

Cisco Security Advisory: Cisco Catalyst Enable Password Bypass Vulnerability

Advisory ID: cisco-sa-20030424-catos

http://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20030424-catos

Revision 1.4

For Public Release 2003 April 24 08:00  UTC (GMT)


Summary

Cisco Catalyst software permits unauthorized access to the enable mode in the 7.5(1) release. Once initial access is granted, access can be obtained for the higher level "enable" mode without a password. This problem is resolved in version 7.6(1). Customers with vulnerable releases are urged to upgrade as soon as possible.

This issue is documented in Cisco Bug ID CSCea42030.

This advisory is posted at http://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20030424-catos.

Affected Products

All users of Cisco Catalyst 4000, 6000, and 6500 with the Catalyst OS software version 7.5(1) only.

No other releases of Cisco Catalyst OS software are affected by this vulnerability. Additionally, Catalyst hardware running Cisco IOS® software is not affected by this vulnerability.

No other Cisco products are affected by this vulnerability.

Vulnerable Products

  • Cisco Catalyst 4000 (Catalyst OS)
  • Cisco Catalyst 6000 (Catalyst OS)
  • Cisco Catalyst 6500 (Catalyst OS)

Products Confirmed Not Vulnerable

No other Cisco products are currently known to be affected by these vulnerabilities.

Details

Anyone who can obtain command line access to an affected switch can bypass password authentication to obtain "enable" mode access without knowledge of the "enable" password. If local user authentication is enabled, any username can be used to gain access to the switch without a valid password. This same local user could then enter enable without a valid password.

Command line access is provided through the console, telnet access, or ssh access methods; http access mode is not affected.

This problem was introduced with the local user authentication feature in software version 7.5(1), and is corrected in version 7.6(1).

This vulnerability is described in Cisco bugid CSCea42030

Vulnerability Scoring Details


Cisco has provided an FAQ to answer additional questions regarding CVSS at
http://www.cisco.com/web/about/security/intelligence/cvss-qandas.html .

Cisco has also provided a CVSS calculator to help compute the environmental impact for individual networks at
http://intellishield.cisco.com/security/alertmanager/cvss .

Impact

Successful exploitation of the vulnerability may result in privilege escalation, and the attacker will be able to access and alter the configuration of the device, including reloading of the device.

Software Versions and Fixes

When considering software upgrades, also consult http://www.cisco.com/go/psirt and any subsequent advisories to determine exposure and a complete upgrade solution.

In all cases, customers should exercise caution to be certain the devices to be upgraded contain sufficient memory and that current hardware and software configurations will continue to be supported properly by the new release. If the information is not clear, contact the Cisco Technical Assistance Center (TAC) or your contracted maintenance provider for assistance.

his vulnerability is fixed  in Catalyst OS version 7.6(1) and later


Workarounds

Use of AAA authentication configurations will eliminate this vulnerability unless configured for fallback to local authentication. AAA configuration information and examples are provided in Configuring TACACS+, RADIUS, and Kerberos on Cisco Catalyst Switches, available at: http://www.cisco.com/en/US/tech/tk59/technologies_tech_note09186a0080094ea4.shtml.

Strictly limiting telnet and/or ssh access to the device will prevent the initial connection required to exploit this vulnerability. Telnet and/or ssh access can be controlled with the following command set:

set ip permit <address> <mask> telnet
set ip permit <address> <mask> ssh  

set ip permit enable

This command set will deny all traffic not specified in the permit statements for each protocol.

Additionally, out-of-band management solutions and isolated management VLAN configurations can help mitigate this vulnerability by limiting the initial access necessary for exploitation.

Obtaining Fixed Software

Cisco has released free software updates that address these vulnerabilities. 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/en/US/docs/general/warranty/English/EU1KEN_.html , or as otherwise set forth at Cisco.com Downloads at http://www.cisco.com/public/sw-center/sw-usingswc.shtml .

Do not contact psirt@cisco.com or security-alert@cisco.com for software upgrades

Customers with Service Contracts

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 Using Third-Party Support Organizations

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 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 Without Service Contracts

Customers who purchase direct from Cisco but 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 acquire 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: tac@cisco.com

Customers should have their product serial number available and be prepared to give the URL of this notice as evidence of entitlement to a free upgrade. Free upgrades for non-contract customers must be requested through the TAC.

Refer to http://www.cisco.com/en/US/support/tsd_cisco_worldwide_contacts.html for additional TAC contact information, including localized telephone numbers, and instructions and e-mail addresses for use in various languages.

Exploitation and Public Announcements

The Cisco PSIRT is not aware of any public announcements or malicious use of the vulnerability described in this advisory.

This vulnerability was reported to Cisco by Marco P. Rodrigues.

Status of This Notice: Final

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.


Distribution

This advisory is posted on Cisco's worldwide website at:

http://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20030424-catos

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
  • full-disclosure@lists.netsys.com
  • first-teams@first.org (includes CERT/CC)
  • cisco@spot.colorado.edu
  • cisco-nsp@puck.nether.net
  • comp.dcom.sys.cisco
  • 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 History

Revision 1.0

24-April-2003

Initial public release.

Revision 1.1

24-April-2003

Added clarification under "Exploitation and Public Announcements" section.

Revision 1.2

25-April-2003

Added customer name that reported issue, corrected details regarding exploitation, and updated workaround information on AAA services.

Revision 1.3

07-May-2003

Added link to AAA configuration examples.

Revision 1.4

05-January-2005

Updated the Configuring TACACS+, RADIUS, and Kerberos on Cisco Catalyst Switches document URL in the Workarounds section.

Cisco Security 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 website at http://www.cisco.com/web/about/security/psirt/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.


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