HIGH
XNU 1228.9.59 and earlier on Apple Mac OS X 10.5.6 and earlier does not properly restrict interaction between user space and the HFS IOCTL handler, which allows local users to overwrite kernel memory and gain privileges by attaching an HFS+ disk image and performing certain steps involving HFS_GET_BOOT_INFO fcntl calls.
http://lists.apple.com/archives/security-announce/2009/Aug/msg00001.html
http://secunia.com/advisories/34424
http://secunia.com/advisories/36096
http://support.apple.com/kb/HT3757
http://www.digit-labs.org/files/exploits/xnu-hfs-fcntl-v2.c
http://www.digit-labs.org/files/exploits/xnu-hfs-fcntl-v2.sh
http://www.informationweek.com/news/hardware/mac/showArticle.jhtml?articleID=216401181
http://www.securityfocus.com/bid/34203
http://www.securitytracker.com/id?1022671
http://www.us-cert.gov/cas/techalerts/TA09-218A.html
http://www.vupen.com/english/advisories/2009/0822