libpcre in PCRE before 8.43 allows a subject buffer over-read in JIT when UTF is disabled, and \X or \R has more than one fixed quantifier, a related issue to CVE-2019-20454.
https://bugs.gentoo.org/717920
http://seclists.org/fulldisclosure/2020/Dec/32
http://seclists.org/fulldisclosure/2021/Feb/14