The do_tkill function in kernel/signal.c in the Linux kernel before 3.8.9 does not initialize a certain data structure, which allows local users to obtain sensitive information from kernel memory via a crafted application that makes a (1) tkill or (2) tgkill system call.
https://bugzilla.redhat.com/show_bug.cgi?id=970873
http://www.ubuntu.com/usn/USN-1900-1
http://www.ubuntu.com/usn/USN-1899-1
http://www.openwall.com/lists/oss-security/2013/06/04/10
http://www.mandriva.com/security/advisories?name=MDVSA-2013:176
http://www.kernel.org/pub/linux/kernel/v3.x/ChangeLog-3.8.9
http://www.debian.org/security/2013/dsa-2766
http://secunia.com/advisories/55055
http://rhn.redhat.com/errata/RHSA-2013-1801.html
http://lists.opensuse.org/opensuse-updates/2013-12/msg00129.html