Last revised: --
Source: CERT/CC
A complete revision history can be found at the end of this file.
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.
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:
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:
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.
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.
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.
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:
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 has published a security advisory describing this vulnerability at
The CERT/CC thanks Cisco Systems for their advisory, on which this
document is based.
Author: Cory F. Cohen
Copyright 2001 Carnegie Mellon University. Revision History
Systems Affected
Overview
I. Description
II. Impact
III. Solution
Upgrade your IOS Release
Disable the HTTP server
Enable TACACS+ or Radius Authentication
Appendix A. - Vendor Information
Cisco Systems
June 28, 2001: Initial release