Out of Bounds Memory Read in unserialize()

How it was found

The finish_nested_data function in ext/standard/var_unserializer.re in PHP before 5.6.31, 7.0.x before 7.0.21, and 7.1.x before 7.1.7 is prone to a buffer over-read while unserializing untrusted data. Exploitation of this issue can have an unspecified impact on the integrity of PHP.

This has been fixed and assigned CVE-2017-12933 the bug report is here: https://bugs.php.net/bug.php?id=74111