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X Font Server: Multiple Vulnerabilities


1.  Gentoo Linux Security Advisory

Version Information

Advisory Reference GLSA 200710-11 / xfs
Release Date October 12, 2007
Latest Revision October 12, 2007: 01
Impact high
Exploitable local
Package Vulnerable versions Unaffected versions Architecture(s)
x11-apps/xfs < 1.0.5 >= 1.0.5 All supported architectures

Related bugreports: #185660, #194606


Three vulnerabilities have been discovered in the X Font Server possibly allowing local attackers to gain elevated privileges.

2.  Impact Information


The X.Org X11 X Font Server provides a standard mechanism for an X server to communicate with a font renderer.


iDefense reported that the xfs init script does not correctly handle a race condition when setting permissions of a temporary file (CVE-2007-3103). Sean Larsson discovered an integer overflow vulnerability in the build_range() function possibly leading to a heap-based buffer overflow when handling "QueryXBitmaps" and "QueryXExtents" protocol requests (CVE-2007-4568). Sean Larsson also discovered an error in the swap_char2b() function possibly leading to a heap corruption when handling the same protocol requests (CVE-2007-4990).


The first issue would allow a local attacker to change permissions of arbitrary files to be world-writable by performing a symlink attack. The second and third issues would allow a local attacker to execute arbitrary code with privileges of the user running the X Font Server, usually xfs.

3.  Resolution Information


There is no known workaround at this time.


All X Font Server users should upgrade to the latest version:

Code Listing 3.1: Resolution

# emerge --sync
# emerge --ask --oneshot --verbose ">=x11-apps/xfs-1.0.5"

4.  References


Page updated October 12, 2007

Summary: This is a Gentoo Linux Security Advisory

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