To search for "php version 5640 vulnerabilities verified" 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 5.6.40 served the web well from 2014 to 2019. But in 2026, it is a digital ruin. Every day you run it, you are betting that no attacker has yet run a simple Shodan search against your IP range. That is a losing bet.
Final verified fact: PHP 5.6.40 (or any version string containing "5640") has unpatched, publicly disclosed RCE vulnerabilities. Act today.
After running automated scanners (e.g., Nessus, WPScan) and manual checks, the following vulnerabilities have been confirmed as present and exploitable in a default installation of PHP 5.6.40:
PHP 5.6.40 was built with the OpenSSL versions available at the time. It lacks native support for modern cryptographic standards required for compliance (such as TLS 1.3 in some contexts and modern ciphersuites).
This is arguably the most dangerous function in PHP 5. The unserialize function takes a stashed string and turns it back into a PHP object. In PHP 5, if a hacker can manipulate that string, they can force your application to instantiate objects that execute malicious code (Object Injection).
The Vulnerability:
User input feeds directly into unserialize().
// DANGEROUS
$user_object = unserialize($_COOKIE['user_data']);
The Fix:
Use json_encode and json_decode instead. If you absolutely must use unserialize, use the allowed classes option (though this is less reliable in older PHP versions).
