AIX crontab VulnerabilityOriginal issue date: May 26, 1992
Last revised: September 19, 1997
Attached copyright statement
A complete revision history is at the end of this file.
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 21:22:40If your crontab contains older modules than the above output indicates, we suggest that you install the fix.
I. DescriptionThe distributed version of /usr/bin/crontab contains a security vulnerability.
II. ImpactLocal users can gain unauthorized root access to the system.
III. SolutionThe 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.
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
If you are on the Internet, use anonymous ftp to obtain the fix from software.watson.ibm.com (18.104.22.168).
Patch Filename Checksum AIX 3.2 pub/aix3/cronta.tar.Z 02324 154The patch must be retrieved using binary mode.
- 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
- Install the fix following the instructions in the README file.
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.
This document is available from: http://www.preview.cert.org/advisories/CA-1992-10.html
CERT/CC Contact Information
CERT Coordination Center
Software Engineering Institute
Carnegie Mellon University
Pittsburgh PA 15213-3890
Phone: +1 412-268-7090 (24-hour hotline)
Fax: +1 412-268-6989
CERT/CC 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.
We strongly urge you to encrypt sensitive information sent by email. Our public PGP key is available from
If you prefer to use DES, please call the CERT hotline for more information.
Getting security information
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Copyright 1992 Carnegie Mellon University.
September 19,1997 Attached copyright statement