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CA-94:11                         CERT Advisory
                                 June 9, 1994
                           Majordomo Vulnerabilities
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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.

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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.


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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.

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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.
