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