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/CC 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.
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If you prefer to use DES, please call the CERT hotline for more
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Getting security information
CERT publications and other security information are available from
our web site
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