ext/snmp/snmp.c in PHP before 5.5.38, 5.6.x before 5.6.24, and 7.x before 7.0.9 improperly interacts with the unserialize implementation and garbage collection, which allows remote attackers to cause a denial of service (use-after-free and application crash) or possibly have unspecified other impact via crafted serialized data, a related issue to CVE-2016-5773.