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 https://sec.cloudapps.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

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.

Fixed Software

• 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

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.

URL

• https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20030424-catos

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.

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