The compile_regex function in pcre_compile.c in PCRE before 8.38 and pcre2_compile.c in PCRE2 before 10.2x mishandles the /(?J:(?|(:(?|(?'R')(\k'R')|((?'R')))H'Rk'Rf)|s(?'R'))))/ and /(?J:(?|(:(?|(?'R')(\z(?|(?'R')(\k'R')|((?'R')))k'R')|((?'R')))H'Ak'Rf)|s(?'R')))/ patterns, and related patterns with certain group references, which allows remote attackers to cause a denial of service (heap-based buffer overflow) or possibly have unspecified other impact via a crafted regular expression, as demonstrated by a JavaScript RegExp object encountered by Konqueror.
https://security.gentoo.org/glsa/201607-02
https://bto.bluecoat.com/security-advisory/sa128
https://access.redhat.com/errata/RHSA-2016:1132
http://www.securityfocus.com/bid/76187