The srandomdev function in Libc in Apple Mac OS X before 10.9, when the kernel random-number generator is unavailable, produces predictable values instead of the intended random values, which makes it easier for context-dependent attackers to defeat cryptographic protection mechanisms by leveraging knowledge of these values, related to a compiler-optimization issue.
http://lists.apple.com/archives/security-announce/2013/Oct/msg00004.html