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AUSCERT External Security Bulletin Redistribution
ESB-2001.267 -- CERT Advisory CA-2001-14
Cisco IOS HTTP Server Authentication Vulnerability
2 July 2001
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AusCERT Security Bulletin Summary
---------------------------------
Product: HTTP Server
Vendor: Cisco Systems
Operating System: Cisco IOS versions 11.3 and later
Impact: Administrator Compromise
Access Required: Remote
Ref: ESB-2001.263
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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
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U.S.A.
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______________________________________________________________________
NO WARRANTY
Any material furnished by Carnegie Mellon University and the Software
Engineering Institute is furnished on an "as is" basis. Carnegie
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_________________________________________________________________
Conditions for use, disclaimers, and sponsorship information
Copyright 2001 Carnegie Mellon University.
Revision History
June 28, 2001: Initial release
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