The Key Distribution Center (KDC) in MIT Kerberos 5 (aka krb5) 1.7 before 1.7.2, and 1.8 alpha, allows remote attackers to cause a denial of service (assertion failure and daemon crash) via an invalid (1) AS-REQ or (2) TGS-REQ request.
http://www.vupen.com/english/advisories/2010/1481
http://www.ubuntu.com/usn/USN-916-1
http://www.securityfocus.com/bid/38260
http://www.securityfocus.com/archive/1/509553/100/0/threaded
http://web.mit.edu/kerberos/advisories/MITKRB5-SA-2010-001.txt
http://support.apple.com/kb/HT4188
http://securitytracker.com/id?1023593
http://secunia.com/advisories/40220
http://secunia.com/advisories/39023
http://secunia.com/advisories/38598
http://lists.fedoraproject.org/pipermail/package-announce/2010-February/035222.html
http://lists.apple.com/archives/security-announce/2010//Jun/msg00001.html