The default configuration of the FreeRADIUS server in Apple Mac OS X Server before 10.6.3 permits EAP-TLS authenticated connections on the basis of an arbitrary client certificate, which allows remote attackers to obtain network connectivity via a crafted RADIUS Access Request message.
http://www.securityfocus.com/bid/39234
http://support.apple.com/kb/HT4077
http://lists.apple.com/archives/security-announce/2010//Mar/msg00001.html