A flaw was found in libpcre. A buffer overread in JIT mode when \X is used in non-UTF mode may cause application crash and denial of service. The flaw is in function doextuninoutf() in pcre2jitcompile.c, which uses the macro GETCHARINC to read a character. However, in case there is an invalid UTF character the value read is too big, which causes an out-of-bounds read in the next statement, while executing macro UCDGRAPHBREAK.

References:

https://bugs.exim.org/showbug.cgi?id=2421 https://bugzilla.redhat.com/showbug.cgi?id=1734468

Upstream patch:

http://git.php.net/?p=php-src.git;a=commitdiff;h=8947fd9e9fdce87cd6c59817b1db58e789538fe9