Apple Mac OS X kernel allows local users to cause a denial of service via a process that uses kevent to register a queue and an event, then fork a child process that uses kevent to register an event for the same queue as the parent.
https://exchange.xforce.ibmcloud.com/vulnerabilities/30544
http://www.vupen.com/english/advisories/2007/3868
http://www.vupen.com/english/advisories/2006/4715
http://www.us-cert.gov/cas/techalerts/TA07-319A.html
http://www.securityfocus.com/bid/26444
http://secunia.com/advisories/27643
http://secunia.com/advisories/23114
http://lists.apple.com/archives/security-announce/2007/Nov/msg00002.html