The scm_check_creds function in net/core/scm.c in the Linux kernel before 3.11 performs a capability check in an incorrect namespace, which allows local users to gain privileges via PID spoofing.
http://www.openwall.com/lists/oss-security/2013/09/05/3
http://www.ubuntu.com/usn/USN-1995-1
http://www.ubuntu.com/usn/USN-1998-1
https://bugzilla.redhat.com/show_bug.cgi?id=1004736
https://github.com/torvalds/linux/commit/d661684cf6820331feae71146c35da83d794467e