PHP 5.6.40 is insecure and should be treated as high risk. Verified vulnerability classes affecting it make continued production use unsafe. Prioritize upgrading to a supported PHP version, and apply mitigations immediately if upgrade cannot be completed right away.
and remains vulnerable to high-severity exploits discovered after its support period Critical Vulnerabilities Affecting PHP 5.6.40 php version 5640 vulnerabilities verified
To search for means you have likely found exactly what you feared: a confirmed, exploitable, unmaintained PHP environment. The verification is not the end of the story—it is the starting gun for emergency modernization. php version 5640 vulnerabilities verified