Published:
26 October 1998
Protect yourself against future threats.
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AUSCERT External Security Bulletin Redistribution
ESB-98.167 -- IBM-ERS Security Vulnerability Alert #1998:004.1
AIX automountd Vulnerability
27 October 1998
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The IBM Emergency Response Service has released the following alert
concerning a vulnerability in the automountd daemon in IBM AIX(r) 4.3.x.
This vulnerability may allow local and remote users to gain root access.
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EMERGENCY RESPONSE SERVICE
SECURITY VULNERABILITY ALERT
26 October 1998 14:00 GMT Number: ERS-SVA-E01-1998:004.1
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VULNERABILITY SUMMARY
VULNERABILITY: The automountd daemon allows local and remote users to become
root.
PLATFORMS: IBM AIX(r) 4.3.x
SOLUTION: Apply the fixes listed below.
THREAT: Remote users can execute arbitrary commands as root.
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DETAILED INFORMATION
I. Description
The automountd daemon processes requests from the local AutoFS filesystem
kernel extension. It uses local files or name service maps to locate file
systems to be mounted. Because the daemon does not verify that requests
are actually from the kernel extension, local non-root users and remote
users can request automountd services.
II. Impact
If the automountd daemon is active, local and remote users can cause
arbitrary commands to run as root. Exploits for this problem have been
made publicly available.
To determine if the daemon is active on your system, run the following
command:
$ lssrc -s automountd
To disable the daemon until the fix can be applied (run as root):
# stopsrc -s automountd
III. Solutions
A. Official fix
IBM is working on the following fixes which will be available soon.
AIX 4.1.x: not vulnerable
AIX 4.2.x: not vulnerable
AIX 4.3.x: IX83752
B. How to alleviate the problem
A temporary fix is available via anonymous ftp from:
ftp://aix.software.ibm.com/aix/efixes/security/automountd.tar.Z
Filename sum md5
==================================================================
autofs.ext 26103 117 4afedf8fbe411e8be2588fa8843211ae
automountd 16386 83 eb4c2e1c4cfe609b2ecba0c6a704640c
NOTE - This temporary fix has not been fully regression tested.
Use the following steps (as root) to install the temporary fix:
1. Determine the version of the NFS fileset on your machine.
# lslpp -l bos.net.nfs.client
The version of the fileset for your machine should be at 4.3.1.4
or higher. If not, install requisite APAR IX81896. This will
help ensure that the temporary fix will run properly.
2. Uncompress and extract the fix.
# uncompress < automountd.tar.Z | tar xf -
# cd automountd
3. Replace the vulnerable executables with the temporary fix.
# (cd /usr/lib/drivers && mv autofs.ext autofs.ext.before_security_fix)
# (cd /usr/sbin && mv automountd automountd.before_security_fix)
# chmod 0 /usr/lib/drivers/autofs.ext.before_security_fix
# chmod 0 /usr/sbin/automountd.before_security_fix
# cp ./autofs.ext /usr/lib/drivers/autofs.ext
# cp ./automountd /usr/sbin/automountd
# chown root.system /usr/sbin/automountd /usr/lib/drivers/autofs.ext
# chmod 555 /usr/sbin/automountd /usr/lib/drivers/autofs.ext
4. Reboot.
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 reference
http://aix.software.ibm.com/support/rs6000
or send email to "aixserv@austin.ibm.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 "aixserv@austin.ibm.com" with
the word "subscribe Security_APARs" in the "Subject:" line.
V. Acknowledgements
Thanks to Repent Security Incorporated for bringing this problem to
our attention. A copy of their autofsd advisory can be found at
http://www.repsec.com/.
VI. Contact Information
Comments regarding the content of this announcement can be directed to
your local IBM support center or to:
security-alert@austin.ibm.com
To request the PGP public key that can be used to encrypt new AIX
security vulnerabilities, send email to security-alert@austin.ibm.com
with a subject of "get key".
If you would like to subscribe to the AIX security newsletter, send a
note to aixserv@austin.ibm.com 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
respective holders.
===============================================================================
IBM's Internet Emergency Response Service (IBM-ERS) is a subscription-based
Internet security response service that includes computer security incident
response and management, regular electronic verification of your Internet
gateway(s), and security vulnerability alerts similar to this one that are
tailored to your specific computing environment. By acting as an extension
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As a part of IBM's Business Recovery Services organization, the IBM Internet
Emergency Response Service is a component of IBM's SecureWay(tm) line of
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SecureWay solutions can give you the assurance and expertise you need to
protect your valuable business resources. To find out more about the IBM
Internet Emergency Response Service, send an electronic mail message to
ers-sales@vnet.ibm.com, or call 1-800-742-2493 (Prompt 4).
IBM-ERS maintains a site on the World Wide Web at http://www.ers.ibm.com/.
Visit the site for information about the service, copies of security alerts,
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IBM-ERS uses Pretty Good Privacy* (PGP*) as the digital signature mechanism for
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"Pretty Good Privacy" and "PGP" are trademarks of Philip Zimmermann.
IBM-ERS is a Member Team of the Forum of Incident Response and Security Teams
(FIRST), a global organization established to foster cooperation and response
coordination among computer security teams worldwide.
Copyright 1998 International Business Machines Corporation.
The information in this document is provided as a service to customers of
the IBM Emergency Response Service. Neither International Business Machines
Corporation, nor any of its employees, makes any warranty, express or implied,
or assumes any legal liability or responsibility for the accuracy, complete-
ness, or usefulness of any information, apparatus, product, or process
contained herein, or represents that its use would not infringe any privately
owned rights. Reference herein to any specific commercial products, process,
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necessarily constitute or imply its endorsement, recommendation or favoring
by IBM or its subsidiaries. The views and opinions of authors expressed
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and may not be used for advertising or product endorsement purposes.
The material in this security alert may be reproduced and distributed,
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This security alert may be reproduced and distributed, without permission,
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increasing the awareness of the Internet community.
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