Date: Wed, 11 Feb 2004 20:45:05 +0000
From: Tim Yamin <[email protected]>
To: [email protected], [email protected],
Subject: [ GLSA 200402-02 ] XFree86 Font Information File Buffer Overflow
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Gentoo Linux Security Advisory GLSA 200402-02
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~ http://security.gentoo.org
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~ Severity: High
~ Title: XFree86 Font Information File Buffer Overflow
~ Date: February 11, 2004
~ ID: 200402-02
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Synopsis
========
Exploitation of a buffer overflow in the XFree86 Project Inc.'s XFree86
X Window System allows local attackers to gain root privileges.
Background
==========
XFree86 provides a client/server interface between display hardware
and the desktop environment while also providing both the windowing
infrastructure and a standardized API. XFree86 is platform
independent, network-transparent and extensible.
Description
===========
Exploitation of a buffer overflow in the XFree86 Window System
discovered by iDefence [ 1 ] allows local attackers to gain root privileges.
The problem exists in the parsing of the 'font.alias' file. The X server
(running as root) fails to check the length of the user provided input,
so a malicious user may craft a malformed 'font.alias' file causing a
buffer overflow upon parsing, eventually leading to the execution of
arbitrary code.
To reproduce the overflow on the command line, you can run:
# cat > fonts.dir <<EOF
~ 1
~ word.bdf \
~ -misc-fixed-medium-r-semicondensed--13-120-75-75-c-60-iso8859-1
~ EOF
# perl -e 'print "0" x 1024 . "A" x 96 . "\n"' > fonts.alias
# X :0 -fp $PWD
{Some output removed}... Server aborting... Segmentation fault (core dumped)
Impact
======
Successful exploitation can lead to a root compromise provided
that the attacker is able to execute commands in the X11
subsystem. This can be done either by having console access to the
target or through a remote exploit against any X client program
such as a web-browser, mail-reader or game.
Workaround
==========
No immediate workaround is available; a software upgrade is required.
Gentoo has released XFree 4.2.1-r3, 4.3.0-r4 and 4.3.99.902-r1 and
encourages all users to upgrade their XFree86 installations. Vulnerable
versions are no longer available in Portage.
Resolution
==========
All users are recommended to upgrade their XFree86 installation:
~ # emerge sync
~ # emerge -pv x11-base/xfree
~ # emerge x11-base/xfree
References
==========
[1] www.idefense.com/application/poi/display?id=72&type=vulnerabilities
Concerns?
=========
Security is a primary focus of Gentoo Linux and ensuring the
confidentiality and security of our users machines is of utmost
importance to us. Any security concerns should be addressed to
[email protected] or alternatively, you may file a bug at
http://bugs.gentoo.org.
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