The pcre_compile function in pcre_compile.c in PCRE before 8.38 mishandles certain [: nesting, which allows remote attackers to cause a denial of service (CPU consumption) or possibly have unspecified other impact via a crafted regular expression, as demonstrated by a JavaScript RegExp object encountered by Konqueror. http://web.nvd.nist.gov/view/vuln/detail?vulnId=CVE-2015-8391