The compilebranch function in pcrecompile.c in PCRE 8.x before 8.39 and pcre2compile.c in PCRE2 before 10.22 mishandles patterns containing an (ACCEPT) substring in conjunction with nested parentheses, which allows remote attackers to execute arbitrary code or cause a denial of service (stack-based buffer overflow) via a crafted regular expression, as demonstrated by a JavaScript RegExp object encountered by Konqueror, aka ZDI-CAN-3542.
Fixed bug (applied upstream patch for CVE-2016-1283).