Multiple buffer overflows in X.org libXxf86dga 1.1.3 and earlier allow X servers to cause a denial of service (crash) and possibly execute arbitrary code via crafted length or index values to the (1) XDGAQueryModes and (2) XDGASetMode functions.
http://www.x.org/wiki/Development/Security/Advisory-2013-05-23
http://www.ubuntu.com/usn/USN-1869-1
http://www.openwall.com/lists/oss-security/2013/05/23/3
http://www.debian.org/security/2013/dsa-2690
http://lists.fedoraproject.org/pipermail/package-announce/2013-May/106870.html