Heap Use After Free in unserialize()

How it was found

ext/standard/var_unserializer.re in PHP 7.0.x before 7.0.21 and 7.1.x before 7.1.7 is prone to a heap use after free while unserializing untrusted data, related to the zval_get_type function in Zend/zend_types.h. Exploitation of this issue can have an unspecified impact on the integrity of PHP.

This has been fixed and assigned CVE-2017-12934. The bug report is here: https://bugs.php.net/bug.php?id=74101