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===========================================================================
             AUSCERT External Security Bulletin Redistribution

                          ESB-2006.0225 -- [AIX]
        A race condition in sendmail may allow a remote attacker to
                          execute arbitrary code.
                               23 March 2006

===========================================================================

        AusCERT Security Bulletin Summary
        ---------------------------------

Product:           sendmail
Publisher:         IBM
Operating System:  AIX 5.1, 5.2 and 5.3
Impact:            Execute Arbitrary Code/Commands
Access:            Remote/Unauthenticated
CVE Names:         CVE-2006-0058

Ref:               AL-2006-0020

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IBM SECURITY ADVISORY


First Issued: Tue Mar 22 10:00:00 CST 2006
==========================================================================
                           VULNERABILITY SUMMARY

VULNERABILITY:      A race condition in sendmail may allow a remote
                    attacker to execute arbitrary code.

PLATFORMS:          AIX 5.1, 5.2 and 5.3.

SOLUTION:           Apply the APAR, interim fix or workaround as
                    described below.

THREAT:             A remote user may execute arbitrary code.

CERT VU Number:     CVE-2006-0058
CVE Number:         VU#834865
=========================================================================
                           DETAILED INFORMATION


I.  Description
===============

A vulnerability was discovered in sendmail that may allow a remote attacker
to execute arbitrary code. This vulnerability is caused by a race condition
that occurs when handling asynchronous signals. Sendmail is a Mail Transfer
Agent that ships with the AIX operating system. It is used for routing mail
for local and network delivery. IBM is providing patches that remove
possible attack vectors for this vulnerability. These patches should be
installed as a precautionary measure.

sendmail ships as part of the bos.net.tcp.client fileset.


II. Impact
==========

A remote attacker may execute arbitrary code with the privileges of the
sendmail daemon. By default, sendmail runs with the privileges of the root
user.


III.  Solutions
===============

A. Official Fix

IBM provides the following fixes:


      APAR number for AIX 5.1.0:  IY82992 (available approx. 07/19/06)
      APAR number for AIX 5.2.0:  IY82993 (available approx. 04/26/06)
      APAR number for AIX 5.3.0:  IY82994 (available approx. 05/10/06)

NOTE: Affected customers are urged to upgrade to the latest applicable
Technology Level.

B. Interim Fix

Interim fixes are available. The ifixes can be downloaded via ftp from:

    ftp://aix.software.ibm.com/aix/efixes/security/sendmail_vu834865.tar.Z

sendmail_vu834865.tar.Z is a compressed tarball containing this advisory,
ifix packages and cleartext PGP signatures for each ifix package.


Verify you have retrieved the fixes intact:
+------------------------------------------
The interim fixes below are named by using the APAR corresponding to the
release that the fix applies to. The APAR is followed by an underscore and
the Technology Level for the particular AIX release that a fix applies to.

The checksums below were generated using the "sum" and "md5sum" commands
and are as follows:

Filename                  sum           md5
========================================================================
IY82992_08.060321.epkg.Z  59022   595   058eae0dfb99d308b6ed682a68e59e23
IY82993_06.060321.epkg.Z  35133   568   171976668510c964aba539601b44d0f2
IY82993_07.060321.epkg.Z  47448   567   ffcdb1d2ade3fd459f7678823100f711
IY82993_08.060321.epkg.Z  01145   568   b2f2828da16b74169dff8c8155e3acda
IY82994_02.060321.epkg.Z  22619   586   2f11241dfc1f1c063491464d64e9c310
IY82994_03.060321.epkg.Z  07719   587   a3bd5bba0a79de02f95debc3916c1fcd
IY82994_04.060321.epkg.Z  44300   588   d310de002540a42dd9b816acf0bc40fc


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 security-alert@austin.ibm.com
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
proceeding.

These ifixes have not been fully regression tested; thus, IBM does not
warrant the fully correct functioning of the ifix. Customers install the
ifix and operate the modified version of AIX at their own risk.

Interim Installation Instructions:
+---------------------------------
These packages use the new Interim Fix Management Solution to install and
manage ifixes. More information can be found at:

     http://www14.software.ibm.com/webapp/set2/sas/f/aix.efixmgmt/home.html

Stop sendmail. This can be done by executing the following command:

# stopsrc -s sendmail

To preview an epkg ifix installation execute the following command:

# emgr -e ipkg_name -p       # where ipkg_name is the name of the
                             # ifix package being previewed.

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

# emgr -e ipkg_name -X       # where ipkg_name is the name of the
                             # ifix package being installed.

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

Start sendmail. This can be done by executing the following command:

# startsrc -s sendmail -a "-bd -q30m"

Verify that sendmail was started:

# lssrc -s sendmail
Subsystem         Group            PID          Status
 sendmail         mail             16000        active


C. Workaround

Turn sendmail off
+----------------
If sendmail is not needed, turn it off. This can be done by using the
stopsrc command:

# stopsrc -s sendmail

Verify that sendmail is no longer running:

# lssrc -s sendmail
Subsystem         Group            PID          Status 
 sendmail         mail                          inoperative

To prevent sendmail from starting on boot, edit the /etc/rc.tcpip startup
script.


Modify sendmail.cf
+----------------
Setting LogLevel to 1 in /etc/sendmail.cf will eliminate some attack vectors
for this vulnerability.


IV. Obtaining Fixes
===================

AIX Version 5 APARs can be downloaded from:

     http://www.ibm.com/servers/eserver/support/unixservers/aixfixes.html

Security related Interim Fixes can be downloaded from:

     ftp://aix.software.ibm.com/aix/efixes/security


V.  Contact Information
=======================

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

     http://www14.software.ibm.com/webapp/set2/subscriptions/pqvcmjd

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

     security-alert@austin.ibm.com

To request the PGP public key that can be used to communicate securely
with the AIX Security Team send email to security-alert@austin.ibm.com
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.
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