-----BEGIN PGP SIGNED MESSAGE----- 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://
/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 -----BEGIN PGP SIGNATURE----- Version: PGPfreeware 5.0i for non-commercial use Charset: noconv iQCVAwUBOztJpAYcfu8gsZJZAQFoOgP/UBtU8yqFbhHf/xD82wCewpBi6NhBAk2M 66WLouQrnXIMWzRWnLmRNV74p+7u+92IxFS/u+TqTzIfByUOtwXLswcRRvHlXYXk 511yHK01wlfgtgv7wwg8doYyCUGPamznNnVEAnbZ/9zoM6Y1nuvUEUgOnvvT9ZMu sCRihIv2WGg= =THYA -----END PGP SIGNATURE-----