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ESB-2005.0174 -- IBM Security Advisory -- A local user may gain root privileges through the perl interpreter

Date: 21 February 2005
References: ESB-2005.0110  

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             AUSCERT External Security Bulletin Redistribution

                  ESB-2005.0174 -- IBM Security Advisory
    A local user may gain root privileges through the perl interpreter
                             21 February 2005


        AusCERT Security Bulletin Summary

Product:           Perl versions 5.8.0 to 5.8.6
Publisher:         IBM
Operating System:  AIX 5.2 and 5.3
                   UNIX variants
                   Linux variants
Impact:            Root Compromise
Access:            Existing Account
CVE Names:         CAN-2005-0156 CAN-2005-0155

Ref:               ESB-2005.0110

- --------------------------BEGIN INCLUDED TEXT--------------------

Hash: SHA1


First Issued: Mon Feb 14 13:26:10 CST 2005

                           VULNERABILITY SUMMARY

VULNERABILITY:      A local user may gain root privileges through the
                    perl interpreter.

PLATFORMS:          AIX 5.2, AIX 5.3

SOLUTION:           Apply the workaround or efix as described below.

THREAT:             A local user may gain root access to a system.

CERT VU Number:     None.
CVE Number:         CAN-2005-0155, CAN-2005-0156
                           DETAILED INFORMATION

I.  Description

Two vulnerabilities were discovered in the perl language interpreter that
may allow a local user to gain root privileges. The perl interpreter is
installed by default in AIX 5.2 and AIX 5.3. Versions of AIX prior to 5.2
do not have perl installed by default and are not vulnerable. Also, these
vulnerabilities occur only in perl with versions 5.8.0 through 5.8.6.

The first vulnerability is through the sperl program which runs perl as an
suid root process. This perl facility is not installed by default on AIX,
but the same vulnerability may exist if perl is invoked by another suid
root program.

The second vulnerability is in the perl interpreter itself and is a buffer
overflow. This is only specific to perl built with threads support, which
is supported in the AIX perl package.

The perl language ships in the perl.rte filesets. To determine if this
fileset is installed, execute the following command:

# lslpp -L perl.rte

If the fileset is installed, it will be listed along with its version
information, state, type and a description.

II. Impact
A local attacker may gain root access to a system.

III.  Solutions

A. Official Fix

Since perl is not an IBM product, only efixes are supplied.

B. Emergency Fix

Efixes are available for AIX 5.3 and AIX 5.2. The efixes can be downloaded
via ftp from:

perl58x.tar.Z is a compressed tarball containing this advisory, two efix
packages for 5.2 and 5.3 and a cleartext PGP signature for each efix
package. The efix package named buff580.021105.epkg.Z contains the fix for
perl version 5.8.0 and is for AIX 5.2. The efix package named
buff582.021105.epkg.Z contains the fix for perl version 5.8.2 and is
for AIX 5.3.

Verify you have retrieved the efixes intact:
- - - ---------------------------------------------
The checksums below were generated using the "sum" and "md5sum" commands
and are as follows:

Filename                 sum          md5
buff580.021105.epkg.Z    20378  5375  8b9cb20e48d4826122bbb047fa0a17ae
buff582.020705.epkg.Z    05026  5580  922e3c706d11d4a464227b92ce8d588e

These sums should match exactly. The PGP signatures in the compressed
tarball and on this advisory can also be used to verify the integrity
of the various files they correspond to. If the sums or signatures cannot
be confirmed, double check the command results and the download site
address. If those are OK, contact IBM AIX Security at and describe the discrepancy.

IMPORTANT: If possible, it is recommended that a mksysb backup of the
system is created. Verify it is both bootable, and readable before

These efixes 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.

Efix Installation Instructions:
- - - --------------------------------
These packages use the new Emergency Fix Management Solution to install
and manage efixes. More information can be found at:

To preview an epkg efix installation execute the following command:

# emgr -e epkg_name -p       # where epkg_name is the name of the
                             # efix package being previewed.

To install an epkg efix package, execute the following command:

# emgr -e epkg_name -X       # where epkg_name is the name of the
                             # efix package being installed.

It is strongly recommended that this efix be mount installed before doing
a regular install. A mount install will mount the patched binaries over
existing system binaries. If any issues arise, the efix can be unmounted
or the system can be rebooted to revert of the original system files. The
mount an epkg efix package, execute the following command:

# emgr -e epkg_name -m       # where epkg_name is the name of the
                             # efix package being installed.

The "X" flag will expand any filesystems if required.

C. Workaround

For the first vulnerability, the workaround would be to disable the suid
bit on any programs on your system that could be executed by a regular
user and also invoked the perl interpreter. Note that this is specific to
your system and does not apply to programs in the perl.rte package. This
may also cause your setuid programs to not function as expected.

# chmod u-s perl_suid_program

For the second vulnerability, the workaround would be to disable the
perl interpreter altogether. Note that this will disable any perl programs
you have on your system. The "x" represents the perl version which
is "0" for AIX 5.2 and "2" for AIX 5.3 .

# chmod 000  /usr/opt/perl5/bin/perl
# chmod 000  /usr/opt/perl5/bin/perl5.8.x
# chmod 000  /usr/opt/perl5/bin/perl_64bit
# chmod 000  /usr/opt/perl5/bin/perl5.8.x_64bit

IV. Obtaining Fixes

Security related Emergency Fixes can be downloaded from:

V. Acknowledgments

The perl vulnerabilities were discovered by Kevin Kinisterre.

This issue was brought to our attention by Campo Weijerman of
IBM Netherlands.

This document was written by Kent Stuiber.

V.  Contact Information

If you would like to receive AIX Security Advisories via email, please

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

To request the PGP public key that can be used to communicate securely
with the AIX Security Team send email to
with a subject of "get key". The key can also be downloaded from a
PGP Public Key Server. The key id is 0x9391C1F2.

Please contact your local IBM AIX support center for any assistance.

eServer is a trademark of International Business Machines Corporation.
IBM, AIX and pSeries are registered trademarks of International Business
Machines Corporation. All other trademarks are property of their
respective holders.

Version: GnuPG v1.2.6 (AIX)


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