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- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - Gentoo Linux Security Advisory GLSA 200402-02 - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - ~ http://security.gentoo.org - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
~ 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 security@gentoo.org or alternatively, you may file a bug at http://bugs.gentoo.org.
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