Apple Filing Protocol (AFP) Server in Apple Mac OS X 10.6.x through 10.6.4 does not properly handle errors, which allows remote attackers to bypass the password requirement for shared-folder access by leveraging knowledge of a valid account name.
https://oval.cisecurity.org/repository/search/definition/oval%3Aorg.mitre.oval%3Adef%3A12109
http://www.securityfocus.com/bid/43341
http://support.apple.com/kb/HT4361
http://lists.apple.com/archives/security-announce/2010/Sep/msg00004.html