Red Hat Security Advisory 2013-1868-01
http://packetstormsecurity.com/files/124527/RHSA-2013-1868-01.txt
Red Hat Security Advisory 2013-1868-01 - X.Org is an open source implementation of the X Window System. It provides the basic low-level functionality that full-fledged graphical user interfaces are designed upon. An integer overflow, which led to a heap-based buffer overflow, was found in the way X.Org server handled trapezoids. A malicious, authorized client could use this flaw to crash the X.Org server or, potentially, execute arbitrary code with root privileges. All xorg-x11-server users are advised to upgrade to these updated packages, which contain a backported patch to correct this issue.