AUSCERT External Security Bulletin Redistribution
     ESB-1999.103 -- IBM-ERS Security Vulnerability Alert #1999:002.1
          IBM AIX: Non-root users can cause the system to crash
                              27 July 1999


The IBM Emergency Response Service has released the following alert
concerning a denial of service vulnerability in the ptrace() system call
of AIX versions 4.2.x and 4.3.x. This vulnerability may allow non-root
users to crash the system.

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                           EMERGENCY RESPONSE SERVICE
                          SECURITY VULNERABILITY ALERT

26 July 1999 15:00 GMT                           Number: ERS-SVA-E01-1999:002.1
                           VULNERABILITY SUMMARY

VULNERABILITY:    Non-root users can cause the system to crash

PLATFORMS:        IBM AIX(r) 4.2.x, 4.3.x

SOLUTION:         Apply the fixes listed below.

                           DETAILED INFORMATION

I.  Description

A denial of service vulnerability has been discovered in the ptrace()
system call of AIX versions 4.2.x and 4.3.x allowing non-root users to
crash the system.  This vulnerability has been posted to the bugtraq
mailing list.

II.  Solutions

  A.  Official fix

    IBM is working on the following fixes which will be available soon.

       AIX 3.2.x:  upgrade to version 4
       AIX 4.1.x:  not vulnerable
       AIX 4.2.x:  IY02381
       AIX 4.3.x:  IY02397

  B.  How to alleviate the problem

    A temporary fix is available via anonymous ftp from:


    Filename                 sum              md5
    unix_mp.42.adb_hang_fix  00772  2693  960214a1945f2c70311283adc0b231a3
    unix_mp.43.adb_hang_fix  15044  3302  584d1c5ea0223110e2d8eba84388f526

    This temporary fix has not been fully regression tested.  The fix
    consists of a multiprocessor kernel which can be used on either a
    uniprocessor or multiprocessor machine.  There may be a slight
    performance penalty when using a multiprocessor kernel on a
    uniprocessor machine.

    Use the following steps (as root) to install the temporary fix:

    1.  Determine the version of the kernel fileset on your machine.

        # lslpp -l <fileset>

        If the version of the kernel fileset for your machine is not at
        the level described below, install the requisite APAR listed.
        This will help ensure that the temporary kernel fix will run

        Release        Fileset            Version        requisite APAR
        AIX 4.2.x      bos.mp or bos.up       IY00689
        AIX 4.3.x      bos.mp or bos.up        IY00727

    2. Uncompress and extract the fix.

        # uncompress < adb_hang.tar.Z | tar xf -
        # cd adb_hang

    3. Review and run the adb_hang.sh script to install the new kernel.

          # view ./adb_hang.sh
          # ./adb_hang.sh

    4. Reboot.

III. 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


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.

IV.  Contact Information

Comments regarding the content of this announcement can be directed to:


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
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To see a list of other available subscriptions, use a subject of

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
of your own internal security staff, IBM-ERS's team of Internet security
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your Internet connection(s).

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@ers.ibm.com, or call 1-800-599-9950.

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 1999 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,
or service by trade name, trademark, manufacturer, or otherwise, does not
necessarily constitute or imply its endorsement, recommendation or favoring
by IBM or its subsidiaries.  The views and opinions of authors expressed
herein do not necessarily state or reflect those of IBM or its subsidiaries,
and may not be used for advertising or product endorsement purposes.

The material in this security alert may be reproduced and distributed,
without permission, in whole or in part, by other security incident response
teams (both commercial and non-commercial), provided the above copyright is
kept intact and due credit is given to IBM-ERS.

This security alert may be reproduced and distributed, without permission,
in its entirety only, by any person provided such reproduction and/or
distribution is performed for non-commercial purposes and with the intent of
increasing the awareness of the Internet community.


Version: 2.7.1


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