The IPv6 implementation in the kernel in Apple Mac OS X before 10.6.8 allows local users to cause a denial of service (NULL pointer dereference and reboot) via vectors involving socket options.
http://www.securityfocus.com/bid/48422
http://support.apple.com/kb/HT4999
http://support.apple.com/kb/HT4723
http://lists.apple.com/archives/security-announce/2011//Jun/msg00000.html
http://lists.apple.com/archives/Security-announce/2011//Oct/msg00001.html