============================================================================= CA-94:11 CERT Advisory June 9, 1994 Majordomo Vulnerabilities ----------------------------------------------------------------------------- The CERT Coordination Center has received reports of vulnerabilities in all versions of Majordomo up to and including version 1.91. These vulnerabilities enable intruders to gain access to the account that runs the Majordomo software, even if the site has firewalls and TCP wrappers. CERT recommends that all sites running Majordomo replace their current version with version 1.92 (see Section III for instructions). It is possible to apply a quick fix to versions prior to 1.92, but we strongly recommend obtaining 1.92 instead. As we receive additional information relating to this advisory, we will place it, along with any clarifications, in a CA-94:11 README file. CERT advisories and their associated README files are available by anonymous FTP from info.cert.org. We encourage you to check the README files regularly for updates on advisories that relate to your site. ----------------------------------------------------------------------------- I. Description Two vulnerabilities have recently been found in Majordomo. These vulnerabilities enable intruders to gain access to the account that runs the Majordomo software, thus gaining the ability to execute arbitrary commands. The vulnerabilities can be exploited without a valid user name and password on the local machine, and firewalls and TCP wrapper protection can be bypassed. CERT has received reports that the vulnerabilities are currently being exploited. II. Impact Intruders can install and execute programs as the user running the Majordomo software. III. Solution A. Recommended solution for all versions through 1.91 Obtain and install Majordomo version 1.92, following the instructions in the README file included with 1.92. This new version is available by anonymous FTP from FTP.GreatCircle.COM and is located in the directory /pub/majordomo as a compressed tar file, majordomo-1.92.tar.Z. This file is also available from ftp.cs.umb.edu in the directory /pub/rouilj and from ftp.pgh.net in the directory /pub/majordomo. BSD SVR4 File Checksum Checksum MD5 Digital Signature ----------------- -------- --------- -------------------------------- majordomo-1.92.tar.Z 55701 223 23408 446 17d9bb9fd4872ab09d01bfeb643b5ebb B. Quick fix for versions 1.91 and earlier Until you are able to install the new version of Majordomo, you should install the following quick fix, which has two steps. If you are running Majordomo 1.90 and earlier, you must take both steps. If you are running version 1.91, you need only take the first step. Step 1 - Disable new-list by either renaming the new-list program or removing it from the aliases file. If you have version 1.90 and earlier, go on to Step 2. Step 2 - In every place in the Majordomo code where there is a string of any of these forms, "|/usr/lib/sendmail -f<whatever> $to" #majordmo.pl "|/usr/lib/sendmail -f<whatever> $reply_to" #request-answer "|/usr/lib/sendmail -f<whatever> \$to" #majordomo.cf Change that string to "|/usr/lib/sendmail -f<whatever> -t" Generally, you will find the strings in the request-answer file, the majordomo.pl file, and your local majordomo.cf file. Note: If you are running a mailer other than sendmail, this step may not fix the vulnerability. You should obtain and install version 1.92 as described in Section A above. --------------------------------------------------------------------------- The CERT Coordination Center thanks Brent Chapman of Great Circle Associates and John Rouillard of the University of Massachusetts at Boston for their support in responding to the problem. --------------------------------------------------------------------------- If you believe that your system has been compromised, contact the CERT Coordination Center or your representative in Forum of Incident Response and Security Teams (FIRST). If you wish to send sensitive incident or vulnerability information to CERT via electronic mail, CERT strongly advises that the e-mail be encrypted. CERT can support a shared DES key, PGP (public key available via anonymous FTP on info.cert.org), or PEM (contact CERT for details). Internet E-mail: cert@cert.org Telephone: 412-268-7090 (24-hour hotline) CERT personnel answer 8:30 a.m.-5:00 p.m. EST(GMT-5)/EDT(GMT-4), and are on call for emergencies during other hours. CERT Coordination Center Software Engineering Institute Carnegie Mellon University Pittsburgh, PA 15213-3890 USA Past advisories, information about FIRST representatives, and other information related to computer security are available for anonymous FTP from info.cert.org.