Multiple integer overflows in X.org libX11 1.5.99.901 (1.6 RC1) and earlier allow X servers to trigger allocation of insufficient memory and a buffer overflow via vectors related to the (1) XQueryFont, (2) _XF86BigfontQueryFont, (3) XListFontsWithInfo, (4) XGetMotionEvents, (5) XListHosts, (6) XGetModifierMapping, (7) XGetPointerMapping, (8) XGetKeyboardMapping, (9) XGetWindowProperty, (10) XGetImage, (11) LoadColornameDB, (12) XrmGetFileDatabase, (13) _XimParseStringFile, or (14) TransFileName functions.
http://www.x.org/wiki/Development/Security/Advisory-2013-05-23
http://www.ubuntu.com/usn/USN-1854-1
http://www.securityfocus.com/bid/60120
http://www.openwall.com/lists/oss-security/2013/05/23/3
http://www.debian.org/security/2013/dsa-2693
http://lists.fedoraproject.org/pipermail/package-announce/2013-May/106781.html