natd in network_cmds in Apple Mac OS X before 10.5.6, when Internet Sharing is enabled, allows remote attackers to cause a denial of service (infinite loop) via a crafted TCP packet.
lists.apple.com/archives/security-announce//2008//Dec/msg00000.html
secunia.com/advisories/33179
support.apple.com/kb/HT3338
www.securityfocus.com/bid/32839
www.securityfocus.com/bid/32874
www.securitytracker.com/id?1021408
www.us-cert.gov/cas/techalerts/TA08-350A.html
www.vupen.com/english/advisories/2008/3444