The SProcXCMiscGetXIDList function in the XC-MISC extension in X.Org X Window System (aka X11 or X) X11R6.0 and X.Org Server (aka xserver and xorg-server) before 1.16.3 allows remote authenticated users to cause a denial of service (out-of-bounds read or write) or possibly execute arbitrary code via a crafted length or index value.
https://security.gentoo.org/glsa/201504-06
http://www.x.org/wiki/Development/Security/Advisory-2014-12-09/
http://www.securityfocus.com/bid/71598
http://www.oracle.com/technetwork/topics/security/cpujul2015-2367936.html
http://www.oracle.com/technetwork/topics/security/bulletinoct2015-2511968.html
http://www.oracle.com/technetwork/topics/security/bulletinjan2015-2370101.html
http://www.debian.org/security/2014/dsa-3095
http://secunia.com/advisories/62292