Open Directory in Apple Mac OS X 10.7 before 10.7.2, when an LDAPv3 server is used with RFC 2307 or custom mappings, allows remote attackers to bypass the password requirement by leveraging lack of an AuthenticationAuthority attribute for a user account.
http://www.securityfocus.com/bid/50085
http://support.apple.com/kb/HT5002
http://lists.apple.com/archives/Security-announce/2011//Oct/msg00003.html