PCRE2 before 10.30 has an out-of-bounds write caused by a stack-based buffer overflow in pcre2_match.c, related to a "pattern with very many captures."
https://vcs.pcre.org/pcre2?view=revision&revision=674
https://vcs.pcre.org/pcre2/code/tags/pcre2-10.30/ChangeLog?revision=854&view=markup
https://security.gentoo.org/glsa/201710-09