CVE 2015-8394
PCRE before 8.38 mishandles the (?(<digits>) and (?(R<digits>) conditions, which allows remote attackers to cause a denial of service (integer overflow) or possibly have unspecified other impact via a crafted regular expression, as demonstrated by a JavaScript RegExp object encountered by Konqueror.
See the 
CVE page on Mitre.org
for more details.
