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[GLSA-200402-02] XFree86 Font Information File Buffer Overflow

Family:

Gentoo Local Security Checks

Category:

infos

Copyright:

(C) 2004 Michel Arboi

Summary:

XFree86 Font Information File Buffer Overflow

Version:

$Revision: 1.1 $

Cve_id:

CAN-2004-0083

Bugtraq_id:

-

Xrefs:

GLSA:200402-02

Description:

The remote host is affected by the vulnerability described in GLSA-200402-02
(XFree86 Font Information File Buffer Overflow)


Exploitation of a buffer overflow in The XFree86 Window System
discovered by iDefence 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 one 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 . "
"' > 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.

References:
http://cve.mitre.org/cgi-bin/cvename.cgi?name=CAN-2004-0083
http://www.idefense.com/application/poi/display?id=72&type=vulnerabilities


Solution:
All users are recommended to upgrade their XFree86 installation:
# emerge sync
# emerge -pv x11-base/xfree
# emerge x11-base/xfree


Risk Factor : High