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TITLE:
X.Org X11 X Font Server Multiple Vulnerabilities

SECUNIA ADVISORY ID:
SA27040

VERIFY ADVISORY:
http://secunia.com/advisories/27040/

CRITICAL:
Less critical

IMPACT:
Privilege escalation

WHERE:
Local system

REVISION:
1.1 originally posted 2007-10-03

SOFTWARE:
X Window System 11 (X11) 7.x
http://secunia.com/product/8806/
X Window System 11 (X11) 6.x
http://secunia.com/product/3913/

DESCRIPTION:
Some vulnerabilities have been reported in the X.Org X11 X Font
Server (XFS), which can be exploited by malicious, local users to
gain escalated privileges.

1) An integer overflow exists within the handlers for the X protocol
requests "QueryXBitmaps" and "QueryXExtents", which do not correctly
check the "length" parameters before passing them to the
"build_range()" function. This can be exploited to cause a heap-based
buffer overflow by sending specially crafted "QueryXBitmaps" and
"QueryXExtents" requests to a vulnerable service.

2) An error exists within the handler for the X protocol requests
"QueryXBitmaps" and "QueryXExtents" when calling the "swap_char2b()"
function, which can be exploited to swap an arbitrary number of bytes
on the heap, resulting in a heap corruption.

Note: On certain systems (e.g. Sun Solaris), these vulnerabilities
may be remotely exploitable through port 7100/TCP.

The vulnerabilities are reported in X.Org XFS 1.0.4 (X11R7.2 and
X11R7.3) and prior.

SOLUTION:
Update to X.Org XFS 1.0.5.

PROVIDED AND/OR DISCOVERED BY:
Sean Larsson, VeriSign iDefense Labs

CHANGELOG:
2007-10-03: Added CVE reference.

ORIGINAL ADVISORY:
X.Org:
http://lists.freedesktop.org/archives/xorg-announce/2007-October/000416.html

iDefense Labs:
http://labs.idefense.com/intelligence/vulnerabilities/display.php?id=602

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