Integer underflow in regcomp.c in Perl before 5.20, as used in Apple OS X before 10.10.5 and other products, allows context-dependent attackers to execute arbitrary code or cause a denial of service (application crash) via a long digit string associated with an invalid backreference within a regular expression.
https://support.apple.com/kb/HT205031
https://security.gentoo.org/glsa/201507-11
http://www.ubuntu.com/usn/USN-2916-1
http://www.securityfocus.com/bid/75704
http://perl5.git.perl.org/perl.git/commit/0c2990d652e985784f095bba4bc356481a66aa06
http://lists.apple.com/archives/security-announce/2015/Aug/msg00001.html