The hfs implementation in Apple Mac OS X 10.5.8 and 10.6.x before 10.6.5 supports hard links to directories and does not prevent certain deeply nested directory structures, which allows local users to cause a denial of service (filesystem corruption) via a crafted application that calls the mkdir and link functions, related to the fsck_hfs program in the diskdev_cmds component.
http://www.securitytracker.com/id?1024723
http://support.apple.com/kb/HT4435
http://lists.apple.com/archives/security-announce/2010//Nov/msg00000.html