ext/standard/var_unserializer.re in PHP before 5.6.26 mishandles object-deserialization failures, which allows remote attackers to cause a denial of service (memory corruption) or possibly have unspecified other impact via an unserialize call that references a partially constructed object.
http://www.openwall.com/lists/oss-security/2016/09/15/10
http://www.php.net/ChangeLog-5.php
http://www.securityfocus.com/bid/93009
http://www.securitytracker.com/id/1036836
https://bugs.php.net/bug.php?id=73052
https://github.com/php/php-src/commit/6a7cc8ff85827fa9ac715b3a83c2d9147f33cd43?w=1
Source: MITRE
Published: 2016-09-17
Updated: 2017-07-30
Type: CWE-119
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