Open Directory in Apple Mac OS X 10.6 before 10.6.4 creates an unencrypted connection upon certain SSL failures, which allows man-in-the-middle attackers to spoof arbitrary network account servers, and possibly execute arbitrary code, via unspecified vectors.
http://www.vupen.com/english/advisories/2010/1481
http://www.securityfocus.com/bid/40871
http://support.apple.com/kb/HT4188
http://securitytracker.com/id?1024103
http://secunia.com/advisories/40220
http://lists.apple.com/archives/security-announce/2010//Jun/msg00001.html