pcre2test.c in PCRE2 10.23 allows remote attackers to cause a denial of service (heap-based buffer overflow) or possibly have unspecified other impact via a crafted regular expression.
https://vcs.pcre.org/pcre2?view=revision&revision=697
https://vcs.pcre.org/pcre2?view=revision&revision=696
https://security.gentoo.org/glsa/201710-09
https://bugs.exim.org/show_bug.cgi?id=2079
https://blogs.gentoo.org/ago/2017/04/29/libpcre-heap-based-buffer-overflow-write-in-pcre2test-c/