c-21.ciac-aix-rexd
9319f1cb5e9d4e866137d9c1ee1fa0b11bd41bb2169e63c31d82628313f007f4
DISTRIBUTION RESTRICTIONS: PUBLIC DISTRIBUTION
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The Computer Incident Advisory Capability
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Information Bulletin
AIX REXD Daemon Vulnerability
March 6, 1992 1000 PST Number C-21
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PROBLEM: In certain configurations the rexd (RPC remote program
execution) daemon is enabled.
PLATFORM: IBM AIX 3.1 and 3.2.
DAMAGE: Anyone can remotely gain access to the system as a user other
than root.
SOLUTION: Apply fix below.
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Critical Facts about AIX REXD Daemon Vulnerability
CIAC has become aware of a possible security problem with the rexd
daemon in versions 3.1 and 3.2 of AIX for IBM RS/6000 machines. In
certain configurations, particularly if NFS is installed, the rexd
(RPC remote program execution) daemon is enabled. Also note that,
installing NFS with the current versions of "mknfs" will re-enable
rexd even if it was previously disabled.
IBM is aware of the problem and will fix it in future updates to AIX
3.1 and 3.2. Sites may call IBM Support (800-237-5511) and ask for
the patch for apar ix21353. Patches may be obtained outside the U.S.
by contacting your local IBM representative.
Until you receive this patch, the following should correct the
problem. IBM and CIAC recommend that sites take the following actions
immediately. These steps should also be taken whenever "mknfs" is
run.
1. Be sure the rexd line in /etc/inetd.conf is commented out by
having a '#' at the beginning of the line:
#rexd sunrpc_tcp tcp wait root /usr/etc/rpc.rexd rexd 100017 1
2. Refresh inetd by running the following command as root:
refresh -s inetd
For additional information or assistance, please contact CIAC:
David Brown
(510) 423-9878/(FTS) 543-9878
dsbrown@llnl.gov
Call CIAC at (510) 422-8193/(FTS) 532-8193 or send e-mail to
ciac@llnl.gov. FAX messages to: (510) 423-8002/(FTS) 543-8002.
Previous CIAC bulletins and other information is available via
anonymous ftp from irbis.llnl.gov (ip address 128.115.19.60).
PLEASE NOTE: Many users outside of the DOE and ESnet computing
communities receive CIAC bulletins. If you are not part of these
communities, please contact your agency's response team to report
incidents. Some of the other teams include the NASA NSI response
team, DARPA's CERT/CC, NAVCIRT, and the Air Force response team. Your
agency's team will coordinate with CIAC.
CIAC would like to thank Darren Reed of the Australian National
University and the Computer Emergency Response Team/Coordination
Center (CERT/CC) for their assistance with this bulletin.
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