IBM Information for VU#466239
IBM AIX line printer daemon contains a buffer overflow in chk_fhost()
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- Statement Date:
- Date Updated: 04 Oct 2001
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11 SEP 2001 0:53 GMT MSS-OAR-E01-2001:391.1
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IBM SECURITY ADVISORY
Fri Sep 7 11:18:24 CDT 2001
VULNERABILITY: Buffer Overflow Vulnerabilities in lpd
PLATFORMS: IBM AIX 4.3 and 5.1
SOLUTION: Apply the emergency-fixes described below.
THREAT: Malicious user could obtain root privileges, or cause
a denial of service (DoS).
CERT Advisory: See CERT CA-2001-15 for info on
Solaris vulnerability. Also see the posting,
http://xforce.iss.net/alerts/advise94.php, at the
Internet Security Systems site for info on BSD
implementations of lpd.
CVE Candidate: CAN-2001-0670
The Line Printer daemon, lpd, shipped with AIX contains several
buffer overflow vulnerabilities that potentially allow a malicious
remote user to gain root privileges.
Two of the three vulnerabilities found require the attacker's system
be listed in /etc/hosts.lpd or /etc/hosts.equiv. The third requires
that the malicious user have control over the victim's domain name
A malicious local or remote user can use a well-crafted exploit code
to gain root privileges on the attacked system, compromising the
integrity of the system and its attached local network.
If the malicious user is unable to gain root access, he or she could
still cause a system crash (DoS) via this vulnerability.
A. Official fix
IBM is working on the following fixes which will be available soon:
AIX 4.3: APAR #IY23037
AIX 5.1: APAR #IY23041
NOTE: Fix will not be provided for versions prior to 4.3 as these
are no longer supported by IBM. Affected customers are urged to
upgrade to 4.3.3 at the latest maintenance level, or to 5.1, when it
B. How to minimize the vulnerability
IBM advises customers to disable the line printer daemon until an
efix or official APAR is installed.
In general, customers are advised to disable all unused daemon
services as good security practice.
EMERGENCY FIX (efix):
Temporary fixes for AIX 4.3.x and 5.1 systems are available.
The temporary fixes can be downloaded via ftp from:
The efix tarball consists of two patched lpd binaries, one for AIX
4.3.x systems (lpd.43) and one for AIX 5.1 (scheduled for release
soon; binary is lpd.51). A copy of this Advisory is also included.
These temporary fixes have not been fully regression tested; thus,
IBM does not warrant the fully correct functioning of the efix.
Customers install the efix and operate the modified version of AIX at
their own risk.
To proceed with efix installation:
First, verify the MD5 cryptographic hash sums of each efix files you
obtain from unpacking the efix tarball with those given below. These
should match exactly; if they do not, double check the hash results
and the download site address. If OK, contact IBM AIX Security at
firstname.lastname@example.org and describe the discrepancy.
Filename sum md5
lpd.43X.tar 11225 20 3c7e6f0ef29b6147835213253de8f1bf
lpd.51B.tar 35507 80 38bc7f7516d76b8a89914fdab97e1377
Efix Installation Instructions:
1. Become root, if not already done.
2. In a scratch or tmp directory, uncompress and untar the efix:
a. uncompress lpd_efix.tar.Z
b. tar -xvf lpd_efix.tar
3. If you are running an AIX 4.3.x system, copy the lpd.43 file to
/usr/sbin. Do the same if you have AIX 5.1 running, except copy the
4. Stop the lpd daemon if it is currently running:
a. stopsrc -s lpd
5. Make a backup copy of the existing lpd binary package in case
something goes wrong with the installation of the efix:
a. cp /usr/sbin/lpd /usr/sbin/lpd.original
6. Now copy the efix binary to take the place of the original lpd:
a. cp /usr/sbin/lpd.43 (or lpd.51, as appropriate)
7. Check to be certain that the new lpd is executable by root and is
assigned proper permissions otherwise.
8. Restart the lpd daemon:
a. startsrc -s lpd
IV. Obtaining Fixes
IBM AIX APARs may be ordered using Electronic Fix Distribution (via
the FixDist program), or from the IBM Support Center. For more
information on FixDist, and to obtain fixes via the Internet, please
or send email to "email@example.com" with the word "FixDist" in
the "Subject:" line.
To facilitate ease of ordering all security related APARs for each
AIX release, security fixes are periodically bundled into a
cumulative APAR. For more information on these cumulative APARs
including last update and list of individual fixes, send email to
"firstname.lastname@example.org" with the word "subscribe Security_APARs" in
the "Subject:" line.
Many thanks to Internet Security Services (ISS) for identifying these
vulnerabilities in lpd, and to the CERT/CC for preparing and
distributing the Vulnerability Notes provided to us vendors.
VI. Contact Information
Comments regarding the content of this announcement can be directed
To request the PGP public key that can be used to encrypt new AIX
security vulnerabilities, send email to email@example.com
with a subject of "get key".
If you would like to subscribe to the AIX security newsletter, send a
note to firstname.lastname@example.org with a subject of "subscribe
Security". To cancel your subscription, use a subject of
"unsubscribe Security". To see a list of other available
subscriptions, use a subject of "help".
IBM and AIX are a registered trademark of International Business
Machines Corporation. All other trademarks are property of their
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