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.
http://blog.checkpoint.com/wp-content/uploads/2016/12/PHP_Technical_Report.pdf
http://www.securityfocus.com/bid/95151
http://www.securitytracker.com/id/1037659
https://access.redhat.com/errata/RHSA-2018:1296
https://bugs.php.net/bug.php?id=73092
Source: MITRE
Published: 2017-01-12
Updated: 2018-05-04
Type: CWE-416
Base Score: 7.5
Vector: AV:N/AC:L/Au:N/C:P/I:P/A:P
Impact Score: 6.4
Exploitability Score: 10
Severity: HIGH
Base Score: 9.8
Vector: CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Impact Score: 5.9
Exploitability Score: 3.9
Severity: CRITICAL