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UNIRAS Brief - 53/04 - OpenBSD Security Bulletin - Reference counting bug in shmat(2)



 
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   UNIRAS (UK Govt CERT) Briefing Notice - 53/04 dated 06.02.04  Time: 11:45
 UNIRAS is part of NISCC(National Infrastructure Security Co-ordination Centre)
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  UNIRAS material is also available from its website at www.uniras.gov.uk and
         Information about NISCC is available from www.niscc.gov.uk
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Title
=====

OpenBSD Security Bulletin:

Reference counting bug in shmat(2)

Detail
====== 

A reference counting bug exists in the shmat(2) system call that
could be used by an attacker to write to kernel memory under certain
circumstances.

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A reference counting bug exists in the shmat(2) system call that
could be used by an attacker to write to kernel memory under certain
circumstances.

The bug, found by Joost Pol, could be used to gain elevated privileges
and has been successfully exploited under FreeBSD.

Patches for OpenBSD 3.4 and 3.3 respectively are also available:

ftp://ftp.openbsd.org/pub/OpenBSD/patches/3.4/common/010_sysvshm.patch
ftp://ftp.openbsd.org/pub/OpenBSD/patches/3.3/common/015_sysvshm.patch

The patch is already present in OpenBSD-current as well as in the
3.3 and 3.4 -stable branches.

For more information on the bug, see Joost Pol's description at:
    http://www.pine.nl/press/pine-cert-20040201.txt


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UNIRAS wishes to acknowledge the contributions of OpenBSD for the information
contained in this Briefing. 
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This Briefing contains the information released by the original author. Some 
of the information may have changed since it was released. If the vulnerability 
affects you, it may be prudent to retrieve the advisory from the canonical site 
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members and the community at large. 
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<End of UNIRAS Briefing>
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