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CA-91:11                        CERT Advisory
                               August 14, 1991
                  ULTRIX LAT/Telnet Gateway Vulnerability

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The Computer Emergency Response Team/Coordination Center (CERT/CC) has
received information concerning a vulnerability in LAT/Telnet gateway
software in Digital Equipment Corporation's (DEC) ULTRIX versions 4.1 
and 4.2 on all architectures.  Information regarding the exploitation
of this vulnerability has been publicly disclosed so we recommend
taking immediate action.  Until you are able to apply the patch we
recommend that sites disable the LAT/telnet service.  

DEC has made a patch available which consists of new /usr/ucb/telnet
binaries.

The patch is available through DEC's Customer Support Centers.  Sites
within the USA should call 1-800-525-7100.  Sites in Europe and elsewhere
should contact DEC through their normal channels.

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I.   DESCRIPTION:

     A vulnerability exists such that ULTRIX 4.1 and 4.2 systems 
     running the LAT/Telnet gateway software can allow unauthorized 
     privileged access.  Although you may not be running the LAT/Telnet
     service at this time, the CERT/CC urges all sites to install 
     the patch.  This will ease any future installation of the
     gateway software.

     The LAT/Telnet software requires special installation and is
     NOT part of the default ULTRIX configuration.

II.  IMPACT:

     Anyone who can access a terminal or modem connected to
     the LAT server running the LAT/Telnet service can gain 
     unauthorized root privileges.

III. SOLUTION:
        
     Obtain the appropriate version of the patch kit for your 
     system architecture from your DEC Customer Support Center,
     and install according to the accompanying instructions.

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The CERT/CC would like to thank George Michaelson of The Prentice Centre,
University of Queensland, Australia and John Annen of Davidson College for 
bringing this to our attention.  We would also like to thank DEC for their 
response to this vulnerability and CIAC for their assistance.
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If you believe that your system has been compromised, contact CERT/CC via
telephone or e-mail.

Computer Emergency Response Team/Coordination Center (CERT/CC)
Software Engineering Institute
Carnegie Mellon University
Pittsburgh, PA 15213-3890

Internet E-mail: cert@cert.org
Telephone: 412-268-7090 24-hour hotline:
           CERT/CC personnel answer 7:30a.m.-6:00p.m. EST,
           on call for emergencies during other hours.

Past advisories and other computer security related information are available
for anonymous ftp from the cert.org (192.88.209.5) system.


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