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ESB-2005.0588 -- OpenBSD Security Advisory -- Another Buffer overflow in zlib

Date: 25 July 2005
References: ESB-2005.0582  ESB-2005.0596  

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

                ESB-2005.0588 -- OpenBSD Security Advisory
                      Another Buffer overflow in zlib
                               25 July 2005

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

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

Product:           zlib
Publisher:         OpenBSD
Operating System:  OpenBSD 3.7 and 3.6
                   UNIX variants
Impact:            Denial of Service
Access:            Remote/Unauthenticated

Ref:               ESB-2005.0582

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

A potential buffer overflow when decoding invalid compressed data
exists in the zlib compression library (installed as libz on OpenBSD).
It is not known at this time whether maliciously-crafted compressed
files can be used to execute arbitrary code but at the very least
there is the potential for a denial of service attack.

Please note that this fixes a different problem that the patch
released two weeks ago.

Since zlib is in wide use throughout the base OS, as well as in
ports, users are advised to patch their systems as soon as possible.

A fix has been committed to OpenBSD-current as well as the 3.6 and
3.7 -stable branches.  Patches are also available for OpenBSD 3.6
and 3.7.  OpenBSD versions 3.4 and lower are not affected as they
use an older version of zlib that does not contain the vulnerable
code.

The main OpenBSD mirror appears to not be updating at the moment, so
the following urls point to the main USA mirror.
3.6 patch:  
    ftp://ftp.usa.openbsd.org/pub/OpenBSD/patches/3.6/common/020_libz.patch
3.7 patch:
    ftp://ftp.usa.openbsd.org/pub/OpenBSD/patches/3.7/common/005_libz.patch

The 3.6 patch also applies to OpenBSD 3.5.

- --------------------------END INCLUDED TEXT--------------------

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This security bulletin is provided as a service to AusCERT's members.  As
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which may arise from following or acting on information or advice contained in
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from the author's website to ensure that the information is still current.

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        http://www.auscert.org.au/render.html?cid=1980

If you believe that your computer system has been compromised or attacked in 
any way, we encourage you to let us know by completing the secure National IT 
Incident Reporting Form at:

        http://www.auscert.org.au/render.html?it=3192

===========================================================================
Australian Computer Emergency Response Team
The University of Queensland
Brisbane
Qld 4072

Internet Email: auscert@auscert.org.au
Facsimile:      (07) 3365 7031
Telephone:      (07) 3365 4417 (International: +61 7 3365 4417)
                AusCERT personnel answer during Queensland business hours
                which are GMT+10:00 (AEST).
                On call after hours for member emergencies only.
===========================================================================

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