A use-after-free in onig_new_deluxe() in regext.c in Oniguruma 6.9.2 allows attackers to potentially cause information disclosure, denial of service, or possibly code execution by providing a crafted regular expression. The attacker provides a pair of a regex pattern and a string, with a multi-byte encoding that gets handled by onig_new_deluxe(). Oniguruma issues often affect Ruby, as well as common optional libraries for PHP and Rust.
https://usn.ubuntu.com/4088-1/
https://support.f5.com/csp/article/K00103182?utm_source=f5support&%3Butm_medium=RSS
https://support.f5.com/csp/article/K00103182
https://security.gentoo.org/glsa/201911-03
https://lists.debian.org/debian-lts-announce/2019/07/msg00013.html
https://github.com/kkos/oniguruma/commit/0f7f61ed1b7b697e283e37bd2d731d0bd57adb55