An out-of-bounds read was discovered in PCRE before 10.34 when the pattern \X is JIT compiled and used to match specially crafted subjects in non-UTF mode. Applications that use PCRE to parse untrusted input may be vulnerable to this flaw, which would allow an attacker to crash the application. The flaw occurs in do_extuni_no_utf in pcre2_jit_compile.c.

• https://bugs.php.net/bug.php?id=78338
• https://bugs.exim.org/show_bug.cgi?id=2421
• https://bugzilla.redhat.com/show_bug.cgi?id=1735494
• https://vcs.pcre.org/pcre2?view=revision&revision=1092
• https://security.gentoo.org/glsa/202006-16
• https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/OQRAHYHLRNMBTPR3KXVM27NSZP3KTOPI/