Directory Services in Apple Mac OS X 10.5.8 and 10.6.x before 10.6.5 does not properly handle errors associated with disabled mobile accounts, which allows remote attackers to bypass authentication by providing a valid account name.
http://www.securitytracker.com/id?1024723
http://www.securityfocus.com/bid/44817
http://support.apple.com/kb/HT4435
http://lists.apple.com/archives/security-announce/2010//Nov/msg00000.html