X.Org X server: Composite local privilege escalation

Background

The X Window System is a graphical windowing system based on a client/server model.

Description

Aaron Plattner discovered a buffer overflow in the compNewPixmap() function when copying data from a large pixel depth pixmap into a smaller pixel depth pixmap.

Impact

A local attacker could execute arbitrary code with the privileges of the user running the X server, typically root.

Workaround

Disable the Composite extension by setting ’ Option “Composite” “disable” ’ in the Extensions section of xorg.conf.

Note: This could affect the functionality of some applications.

Resolution

All X.Org X server users should upgrade to the latest version:

 # emerge --sync
 # emerge --ask --oneshot --verbose ">=x11-base/xorg-server-1.3.0.0-r1"