This indicates an attack attempt to exploit a Stack Buffer Overflow Vulnerability in PHP.
The vulnerability is due to an error in the vulnerable application when handling a maliciously crafted request. A remote attacker may be able to exploit this to cause an information disclosure or denial of service condition on the affected system.
PHP Group PHP 5.6.33 and prior
PHP Group PHP 7.0.x before 7.0.28
PHP Group PHP 7.1.x through 7.1.14
PHP Group PHP 7.2.x through 7.2.2
Information Disclosure: Remote attackers can gain sensitive information from vulnerable systems.
Denial of Service: Remote attackers can crash vulnerable systems.
Apply the most recent upgrade or patch from the vendor: