This indicates an attack attempt to exploit a Denial of Service vulnerability in PHP.
The vulnerability is due to an error when the vulnerable software handles a maliciously crafted serialized object. A remote attacker may be able to exploit this to cause a denial of service condition on a affected system.
PHP Group PHP 5.6.x up to 5.6.29
PHP Group PHP 7.0.x up to 7.0.13
Denial of Service: Remote attackers can crash vulnerable systems.
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