Heap Use After Free Read in unserialize()

How it was found

ext/standard/var_unserializer.re in PHP 7.0.x through 7.0.22 and 7.1.x through 7.1.8 is prone to a heap use after free while unserializing untrusted data, related to improper use of the hash API for key deletion in a situation with an invalid array size. Exploitation of this issue can have an unspecified impact on the integrity of PHP.

This is CVE-2017-12932 and the bug report confirming that I reported the issue is here: https://bugs.php.net/bug.php?id=74103