GNOME GDM 2.8, 2.12, 2.14, and 2.15, when the "face browser" feature is enabled, allows local users to access the "Configure Login Manager" functionality using their own password instead of the root password, which can be leveraged to gain additional privileges.
https://exchange.xforce.ibmcloud.com/vulnerabilities/27018
http://www.vupen.com/english/advisories/2006/2239
http://www.securityfocus.com/bid/18332
http://www.securityfocus.com/archive/1/436428
http://www.mandriva.com/security/advisories?name=MDKSA-2006:100
http://www.gentoo.org/security/en/glsa/glsa-200606-14.xml
http://secunia.com/advisories/20636
http://secunia.com/advisories/20627
http://secunia.com/advisories/20587
http://secunia.com/advisories/20552
http://secunia.com/advisories/20532
http://lists.suse.com/archive/suse-security-announce/2006-Jun/0003.html