This indicates an attack attempt to exploit a Code Execution vulnerability in PHP exif extension.
The vulnerability is due to an error in the application when handling a maliciously crafted file. A remote attacker may be able exploit this to execute arbitrary code within the context of the application via a crafted file.
PHP Group PHP prior to 5.4.37
PHP Group PHP prior to 5.5.21
PHP Group PHP prior to 5.6.5
System Compromise: Remote attackers can gain control of vulnerable systems.
Apply the most recent upgrade or patch from the vendor.