PCRE before 8.36 mishandles the /((?(R)a|(?1)))+/ pattern and related patterns with certain recursion, which allows remote attackers to cause a denial of service (segmentation fault) or possibly have unspecified other impact via a crafted regular expression, as demonstrated by a JavaScript RegExp object encountered by Konqueror.
Heap-based buffer overflow in PCRE 8.36 and earlier allows remote attackers to cause a denial of service (crash) or have other unspecified impact via a crafted regular expression, related to an assertion that allows zero repeats.