Archive of CERT general posting, CERT Advisory CA-2001-14

29/06/01, CERT Advisory CA-2001-14
From: CERT Advisory <cert-advisory@cert.org>

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To: cert-advisory@cert.org
Subject: CERT Advisory CA-2001-14
From: CERT Advisory <cert-advisory@cert.org>
Date: Thu, 28 Jun 2001 11:21:48 -0400 (EDT)
Organization: CERT(R) Coordination Center - +1 412-268-7090


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CERT Advisory CA-2001-14 Cisco IOS HTTP Server Authentication Vulnerability

   Original release date: June 28, 2001
   Last revised: --
   Source: CERT/CC

   A complete revision history can be found at the end of this file.

Systems Affected

     * Cisco IOS systems using local authentication databases with the
       HTTP server enabled

Overview

   A problem with the HTTP server component of Cisco IOS system software
   allows an intruder to execute privileged commands on Cisco routers if
   local authentication databases are used.

I. Description

   By sending a particular URL to a Cisco IOS device with the HTTP server
   enabled, a remote attacker may be able to execute commands at the
   highest privilege level (15). The malicious URL is of the following
   form:

          http://<address>/level/XX/exec/...

   The value of XX is a number between 16 and 99. While a single
   malicious URL will not work consistently against all devices, the
   limited number of possible URLs can allow an attacker to try each URL
   until the attack succeeds.

   This problem occurs if the system is using a local authentication
   database, but not if the Terminal Access Controller Access Control
   System (TACACS+) or Radius authentication systems are used.

   Cisco has published a security advisory describing this vulnerability
   and its solutions, in more detail at:

          http://www.cisco.com/warp/public/707/IOS-httplevel-pub.html

II. Impact

   A remote attacker can execute arbitrary commands at the highest
   privilege level (15) on systems using local authentication databases
   with the HTTP server enabled. This access allows a remote attacker to
   inspect or change the configuration of the device, effectively
   allowing complete control.

III. Solution

Upgrade your IOS Release

   Cisco has published detailed information about upgrading affected
   Cisco IOS software to correct this vulnerability. System managers are
   encouraged to upgrade to one of the non-vulnerable releases.

Disable the HTTP server

   Because this problem exists in the handling of HTTP requests,
   disabling the HTTP server prevents the vulnerability from being
   exploited. Information about disabling the HTTP server is provided in
   the Cisco security advisory on this topic.

Enable TACACS+ or Radius Authentication

   This vulnerability is not present when the Terminal Access Controller
   Access Control System (TACACS+) or Radius authentication systems are
   used. Enabling one of these authentication mechanisms in place of
   local authorization databases will prevent the vulnerability from
   being exploited. Information about enabling TACACS+ or Radius can be
   found in the following Cisco document:

          http://www.cisco.com/warp/public/480/tacplus.shtml

Appendix A. - Vendor Information

   This appendix contains information provided by vendors for this
   advisory. When vendors report new information to the CERT/CC, we
   update this section and note the changes in our revision history. If a
   particular vendor is not listed below, we have not received their
   comments.

Cisco Systems

   Cisco has published a security advisory describing this vulnerability
   at

          http://www.cisco.com/warp/public/707/IOS-httplevel-pub.html
     _________________________________________________________________

   The CERT/CC thanks Cisco Systems for their advisory, on which this
   document is based.
     _________________________________________________________________

   Author: Cory F. Cohen
   ______________________________________________________________________

   This document is available from:
   http://www.cert.org/advisories/CA-2001-14.html
   ______________________________________________________________________

CERT/CC Contact Information

   Email: cert@cert.org
          Phone: +1 412-268-7090 (24-hour hotline)
          Fax: +1 412-268-6989
          Postal address:
          CERT Coordination Center
          Software Engineering Institute
          Carnegie Mellon University
          Pittsburgh PA 15213-3890
          U.S.A.

   CERT personnel answer the hotline 08:00-17:00 EST(GMT-5) / EDT(GMT-4)
   Monday through Friday; they are on call for emergencies during other
   hours, on U.S. holidays, and on weekends.

Using encryption

   We strongly urge you to encrypt sensitive information sent by email.
   Our public PGP key is available from

   http://www.cert.org/CERT_PGP.key

   If you prefer to use DES, please call the CERT hotline for more
   information.

Getting security information

   CERT publications and other security information are available from
   our web site

   http://www.cert.org/

   To subscribe to the CERT mailing list for advisories and bulletins,
   send email to majordomo@cert.org. Please include in the body of your
   message

   subscribe cert-advisory

   * "CERT" and "CERT Coordination Center" are registered in the U.S.
   Patent and Trademark Office.
   ______________________________________________________________________

   NO WARRANTY
   Any material furnished by Carnegie Mellon University and the Software
   Engineering Institute is furnished on an "as is" basis. Carnegie
   Mellon University makes no warranties of any kind, either expressed or
   implied as to any matter including, but not limited to, warranty of
   fitness for a particular purpose or merchantability, exclusivity or
   results obtained from use of the material. Carnegie Mellon University
   does not make any warranty of any kind with respect to freedom from
   patent, trademark, or copyright infringement.
     _________________________________________________________________

   Conditions for use, disclaimers, and sponsorship information

   Copyright 2001 Carnegie Mellon University.

   Revision History
June 28, 2001:  Initial release

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