Oniguruma through 6.9.3, as used in PHP 7.3.x and other products, has a heap-based buffer over-read in str_lower_case_match in regexec.c.
bugs.php.net/bug.php?id=78559
github.com/kkos/oniguruma/commit/d3e402928b6eb3327f8f7d59a9edfa622fec557b
lists.debian.org/debian-lts-announce/2019/12/msg00002.html
lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/NO267PLHGYZSWX3XTRPKYBKD4J3YOU5V/
usn.ubuntu.com/4460-1/