The (1) S_reghop3, (2) S_reghop4, and (3) S_reghopmaybe3 functions in regexec.c in Perl before 5.24.0 allow context-dependent attackers to cause a denial of service (infinite loop) via crafted utf-8 data, as demonstrated by a\x80. http://web.nvd.nist.gov/view/vuln/detail?vulnId=CVE-2015-8853
