The kernel in Apple OS X before 10.10.5 does not properly mount HFS volumes, which allows local users to cause a denial of service via a crafted volume.
http://lists.apple.com/archives/security-announce/2015/Aug/msg00001.html
http://lists.apple.com/archives/security-announce/2015/Sep/msg00001.html
http://lists.apple.com/archives/security-announce/2015/Sep/msg00005.html
https://support.apple.com/HT205212
https://support.apple.com/HT205213