CERT Advisory 046

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CERT Advisory

 · 4 years ago

  

 
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CA-92:10                        CERT Advisory 
                                May 26, 1992 
                          AIX crontab Vulnerability 

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The Computer Emergency Response Team/Coordination Center (CERT/CC) has 
received information concerning a vulnerability in crontab(1) in version 3.2 
of IBM's AIX operating system. 

IBM is aware of this problem and a fix is available as apar number "ix26997" 
for AIX version 3.2.  The version information for the patched /usr/bin/crontab 
is shown in the following what(1) output: 

% what /usr/bin/crontab 
04 1.23 com/cmd/cntl/cron/crontab.c, cmdcntl, bos320, 9218320f 4/8/92 11:50:42 
07 1.8  com/cmd/cntl/cron/permit.c, bos, bos320 4/25/91 17:16:59 
11 1.15  com/cmd/cntl/cron/cronsub.c, bos, bos320 8/18/91 20:42:32 
06 1.9  com/cmd/cntl/cron/funcs.c, bos, bos320 6/8/91 21:22:40 

If your crontab contains older modules than the above output indicates, we 
suggest that you install the fix. 

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I.   Description 

     The distributed version of /usr/bin/crontab contains a security 
     vulnerability. 
      

II.  Impact 

     Local users can gain unauthorized root access to the system. 

 
III. Solution 

      The CERT/CC suggests that sites install the fix that IBM has made 
      available.  As an interim step, we suggests that sites prevent all 
      non-root users from running /usr/bin/crontab by removing (or renaming) 
      the /var/adm/cron/cron.allow and /var/adm/cron/cron.deny files. 

      - Obtain the fix from IBM Support. 

           1. To order from IBM call 1-800-237-5511 and ask 
              that the fix be shipped.  Patches may be obtained 
              outside the U.S. by contacting your local IBM 
              representative. 

           2. If you are on the Internet, use anonymous ftp to obtain 
              the fix from software.watson.ibm.com (129.34.139.5). 

              Patch           Filename                Checksum 
              AIX 3.2         pub/aix3/cronta.tar.Z   02324   154 

              The patch must be retrieved using binary mode. 

      - Install the fix following the instructions in the README file. 

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The CERT/CC would like to thank Fuat Baran of Advanced Network & Services, 
Inc. for bringing this security vulnerability to our attention and IBM for 
their quick response to this problem. 
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If you believe that your system has been compromised, contact CERT/CC or 
your representative in FIRST (Forum of Incident Response and Security Teams). 

Internet E-mail: cert@cert.org 
Telephone: 412-268-7090 (24-hour hotline) 
           CERT/CC personnel answer 7:30 a.m.-6:00 p.m. EST(GMT-5)/EDT(GMT-4), 
           on call for emergencies during other hours. 

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

Past advisories, information about FIRST representatives, and other 
information related to computer security are available for anonymous ftp 
from cert.org (192.88.209.5). 

 
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