For system administrators who need to verify the status of their PHP installations, several methods can confirm if a system is vulnerable.

Deploy a WAF (such as Cloudflare, AWS WAF, or ModSecurity) in front of your server. Configure rules specifically designed to block:

To protect your website from PHP vulnerabilities, follow these best practices:

You can use this for an internal security report, a system admin log, or a client advisory.

Directory traversal patterns attempting to access underlying system binaries. 4. Containerization and Isolation

Although 5.6.40 patched these specific bugs, running it today is highly discouraged by the PHP Development Team because: PHP 5.6.40 Release Announcement

While often associated with newer versions, certain configurations of PHP-FPM on Nginx servers remain a high-risk factor for older stacks.

Place the server behind a strict reverse proxy and restrict network access.

A heap-based buffer overflow exists in the gdImageColorMatch function. Attackers can trigger this by calling the function with crafted image data, which can lead to application crashes or arbitrary code execution.

PHP version was the final release of the PHP 5.6 branch, which reached its end-of-life (EOL) on December 31, 2018 . Despite being a maintenance release intended to address final security concerns, it remains vulnerable to several critical flaws discovered post-release. Verified Vulnerabilities in PHP 5.6.40

PHP 5.6.40 was released before modern cryptography became the standard. It relies on libraries that are now considered weak.

On Debian-based systems, the dpkg -l | grep php command will show the version of installed PHP packages. For Debian 8 "Jessie", a version of 5.6.40+dfsg-0+deb8u2 or higher would indicate that the fixes for the March 2019 vulnerabilities are in place. Updates addressing the issues from 2020 would be at version 5.6.40+dfsg-0+deb8u11 or higher.

If a hacker controls a string input and you compare it to a hash or a number, PHP 5 might convert it unexpectedly.