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IBM AIX NLS Buffer Overflow Vulnerability



                       The U.S. Department of Energy
                    Computer Incident Advisory Capability
                           ___  __ __    _     ___
                          /       |     /_\   /
                          \___  __|__  /   \  \___

                             INFORMATION BULLETIN

                       NLS Buffer Overflow Vulnerability

April 24, 1997 21:00 GMT                                           Number H-49
PROBLEM:       A vulnerability exists in libraries using Natural Language
               Service (NLS).
PLATFORM:      AIX 4.2 and earlier
               Linux libc 5.3.12 and earlier
DAMAGE:        Local and possibility remote users may gain root privileges.
SOLUTION:      Take the steps outlined in Section III as soon as possible.
VULNERABILITY  Exploit details involving this vulnerability have been made
ASSESSMENT:    publicly available.

[******  Start CERT Advisory  ******]

CERT* Advisory CA-97.10
Original issue date: April 24, 1997
Last revised: --
Topic: Vulnerability in Natural Language Service
- ------------------------------------------------------------------------------

The CERT Coordination Center has received reports of a buffer overflow
condition that affects some libraries using the Natural Language Service (NLS)
on UNIX systems. By exploiting this vulnerability, any local user can execute
arbitrary programs as a privileged user. There is a possibility (with some old
libraries) that the vulnerability can be exploited by a remote user.

Exploitation information is publicly available.

The CERT/CC team recommends installing patches when they become available.

We will update this advisory as we receive additional information.
Please check advisory files regularly for updates that relate to your site.

- ------------------------------------------------------------------------------

I.   Description

     A buffer overflow condition affects libraries using the Natural Language
     Service (NLS). The NLS is the component of UNIX systems that provides
     facilities for customizing the natural language formatting for the
     system. Examples of the types of characteristics that can be set are
     language, monetary symbols and delimiters, numeric delimiters, and time

     Some libraries that use a particular environment variable associated with
     the NLS contain a vulnerability in which a buffer overflow condition can
     be triggered. The particular environment variable involved is NLSPATH on
     some systems and PATH_LOCALE on others.

     It is possible to exploit this vulnerability to attain unauthorized
     access by supplying carefully crafted arguments to programs that are
     owned by a privileged user-id and that have setuid or setgid bits set.

     Exploit information involving this vulnerability has been made
     publicly available.

II.  Impact

     Local users (users with access to an account on the system) are able to
     execute arbitrary programs as a privileged user without authorization.
     There is a possibility (with some old libraries) that the vulnerability
     can be exploited by a remote user.

III. Solution

     Install a patch for this problem when one becomes available.
     Currently, there is no workaround to use in the meantime.

     Below is a list of vendors who have provided information about this
     problem. Details are in Appendix A of this advisory; we will update the
     appendix as we receive more information. If your vendor's name is not on
     this list, the CERT/CC did not hear from that vendor. Please contact your
     vendor directly.

        Berkeley Software Design, Inc. (BSDI)
        Cray Research - A Silicon Graphics Company
        Data General Corporation
        Digital Equipment Corporation
        Hewlett-Packard Company
        IBM Corporation
        Linux Systems
        NEC Corporation
        The Santa Cruz Operation (SCO)
        Sun Microsystems, Inc.

- ------------------------------------------------------------------------
Appendix A - Vendor Information

Below is a list of the vendors who have provided information for this
advisory. We will update this appendix as we receive additional information.
If you do not see your vendor's name, the CERT/CC did not hear from that
vendor. Please contact the vendor directly.

Berkeley Software Design, Inc. (BSDI)
  No versions of BSD/OS are vulnerable to this problem.

Cray Research - A Silicon Graphics Company
  We're investigating.

Data General Corporation
  We're investigating.

Digital Equipment Corporation

   Digital Equipment Corporation                        
   Software Security Response Team
   Copyright (c) Digital Equipment Corporation 1997. All rights reserved.

    This reported problem is not present for Digital's ULTRIX or
    Digital UNIX Operating Systems Software.

Hewlett-Packard Company
  Investigation in process, results -to date- indicate HP not
  vulnerable. This advisory will be updated when investigation is complete.

IBM Corporation
  All AIX releases are vulnerable to a variation of this advisory.

  AIX 3.2.5

    Apply the following fix to your system:

    PTFs - U447656 U447671 U447676 U447682 U447705 U447723  (APAR IX67405)

    To determine if you have these PTFs on your system, run the following

       lslpp -lB U447656 U447671 U447676 U447682 U447705 U447723

  AIX 4.1

    Apply the following fix to your system:

        APAR - IX67407

    To determine if you have this APAR on your system, run the following

       instfix -ik IX67407

    Or run the following command:
       lslpp -h bos.rte.libc

    Your version of bos.rte.libc should be or later.

  AIX 4.2
    Apply the following fixes to your system:

        APAR - IX67377 IX65693

    To determine if you have these APARs on your system, run the following

       instfix -ik IX67377 IX65693

    Or run the following command:
       lslpp -h bos.rte.libc

    Your version of bos.rte.libc should be or later.

    (APAR IX65693 fixes a problem with the mkgroup command after IX67377
    is applied.)

  To Order
    APARs may be ordered using Electronic Fix Distribution (via FixDist)
    or from the IBM Support Center.  For more information on FixDist,
    reference URL:


    or send e-mail to aixserv@austin.ibm.com with a subject of "FixDist".

  IBM and AIX are registered trademarks of International Business Machines

Linux Systems
  Linux systems running older C libraries are vulnerable. To check which C
  library is being used type

  linux% ldd /bin/ls
          libc.so.5 => /lib/libc.so.5.3.12

  This indicates the machine is using libc 5.3.12.

  C libraries older than 5.3.12 (that is libc5.2.18, libc5.0.9 etc) are
  vulnerable to this bug and you should upgrade the C library. The release
  versions of libc 5.4.x are immune to this attack.

  If you have libc5.3.12 it is insecure unless it is the modified
  libc5.3.12 shipped with Red Hat 4.1, or as an upgrade on Red Hat 4.0. You
  can check this with the package manager:

  linux# rpm -q libc

  Indicates you have version 17 of the package. This is the safe one.

  Red Hat 4.0 users who have not already upgraded their libc can obtain
  this package at


NEC Corporation
  NEC platforms are not affected by this vulnerability.

  No versions of NeXTstep of OpenStep/Mach are vulnerable to this problem.

The Santa Cruz Operation (SCO)
  We are investigating this problem and will provide updated information
  for this advisory when it becomes available.

  Solbourne is not vulnerable.

Sun Microsystems, Inc.
  Not vulnerable.

[******  End CERT Advisory  ******]


CIAC wishes to acknowledge the contributions of CERT and Wolfgang Ley of DFN-
CERT for the information contained in this bulletin.

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