In all versions of PHP 7, during the unserialization process, resizing the 'properties' hash table of a serialized object may lead to use-after-free. A remote attacker may exploit this bug to gain arbitrary code execution.
https://www.youtube.com/watch?v=LDcaPstAuPk
https://security.netapp.com/advisory/ntap-20180112-0001/
https://bugs.php.net/bug.php?id=73092
https://access.redhat.com/errata/RHSA-2018:1296
http://www.securitytracker.com/id/1037659