A double free issue existed in the handling of Mach ports.
This issue was addressed through improved validation of Mach ports.
CVE-2014-4375 : an anonymous researcher.
Well, I’ve known this bug for a while and it was insanely fun as anti-debugging measure because of its random effects when triggered. For example, sometimes you get an immediate kernel panic, others nothing happens, and most of the time you get weird CPU spikes not attributed to any process, or system lock ups after a while.