K-034: Cisco Catalyst Enable Password Bypass Vulnerability

PROBLEM:       Cisco Catalyst software permits unauthorized access to the
               enable mode. Once initial access is granted, access can be
               obtained for a higher level "enable" mode without a password.
PLATFORM:      All users of Cisco Catalyst 4000, 5000, 5500, 6000 and 6500
               with the software version 5.4(1) only.
DAMAGE:        This vulnerability permits unauthorized access to the
               configuration mode and unauthorized configuration changes on a
               Catalyst switch.
SOLUTION:      There are no known workarounds for this vulnerability. Upgrade
               to version 5.4(2).
VULNERABILITY  The risk is medium. Cisco Systems knows of no public discussion
ASSESSMENT:    nor active exploits involving this vulnerability. However,
               several customers have reportedly encountered this
               vulnerability during NORMAL use.


[Start Cisco Systems Advisory]


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Cisco Catalyst Enable Password Bypass Vulnerability

Revision 1.1

Tentatively for release 2000 April 19 08:00 AM US/Pacific (UTC+0700)

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Summary
=======

Cisco Catalyst software permits unauthorized access to the enable mode in
the 5.4(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 5.4(2). Customers with vulnerable releases are urged to
upgrade as soon as possible.

This vulnerability has been assigned Cisco bug ID CSCdr10025.


Affected Products
=================

All users of Cisco Catalyst 4000, 5000, 5500, 6000 and 6500 with the
software version 5.4(1) only.

The affected image names are as follows:
    cat4000_5-4-1.bin
    cat5000-supg_5-4-1.bin
    cat5000-Sup_5-4-1.bin
    cat5000-Sup3_5-4-1.bin
    cat6000-Sup_5-4-1.bin

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


Details
=======

Anyone who can obtain ordinary console access to an affected switch can
bypass password authentication to obtain "enable" mode access without
knowledge of the "enable" password. This vulnerability can be exploited
through the network using telnet or via the physical console.

This problem was introduced in software version 5.4(1), and is corrected in
version 5.4(2). Due to this defect, software version 5.4(1) is deferred.
Customers are urged to upgrade to version 5.4(2).


Impact
======

This vulnerability permits unauthorized access to the configuration mode and
unauthorized configuration changes on a Catalyst switch.


Software Versions and Fixes
===========================

Getting Fixed Software
======================

Cisco is offering free software upgrades to remedy this vulnerability for
all affected customers.

Customers with contracts should obtain upgraded software through their
regular update channels. For most customers, this means that upgrades should
be obtained via the Software Center on Cisco's Worldwide Web site at
http://www.cisco.com.

Customers without contracts 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: tac@cisco.com

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.


Workarounds
===========

There are no known workarounds for this vulnerability.  Strictly limiting
telnet access to the device will prevent the initial connection required to
exploit this vulnerability. Telnet access can be controlled with the
following command set:

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

This command set will deny all traffic not specified in the permit
statement.


Exploitation and Public Announcements
=====================================

Cisco Systems knows of no public discussion nor active exploits involving
this vulnerability, which was reported by several customers who encountered
it during normal use.


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 facts have been checked to the best of
our ability. Cisco does not anticipate issuing updated versions of this
notice unless there is some material change in the facts. Should there be a
significant change in the facts, Cisco may update this notice.


Distribution
============

This notice will be posted on Cisco's Worldwide Web site
at http://www.cisco.com/warp/public/707/catos-enable-bypass-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
   * first-teams@first.org (includes CERT/CC)
   * cisco@spot.colorado.edu
   * comp.dcom.sys.cisco
   * Various internal Cisco mailing lists

Future updates of this notice, if any, will be placed on Cisco's Worldwide
Web server, 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 1.0 For public release 19-APR-2000 08:00 AM US/Pacific (UTC+0700)
 Revision 1.1 For public release 19-APR-2000 08:00 AM US/Pacific (UTC+0700)


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
Web site at
http://www.cisco.com/warp/public/707/sec_incident_response.shtml. This
includes instructions for press inquiries regarding Cisco security notices.
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This notice is copyright 2000 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.
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All contents copyright (c) 1992--2000 Cisco Systems Inc. Important Notices and
Privacy Statement.

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[End Cisco Systems Advisory]

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