If you arrived here looking for , you now have a comprehensive set of URLs:
While PHP 5.6.40 was the final security release for the 5.6 branch, it is still susceptible to numerous unpatched flaws and inherited issues. Key risks include: Remote Code Execution (RCE): Flaws in core extensions like ext/session
The U.S. government's repository of standards-based vulnerability management data. Search the NVD CVE Portal using the keyword "PHP" to view active listings.
To audit, track, and analyze these specific flaws, utilize the following official security repositories:
These are just a fraction of the ~250+ vulnerabilities reported since 5.6.40's EOL. php version 5640 vulnerabilities link
: The official PHP website often has a section on security where you can find information on known vulnerabilities, how to report them, and advisories.
There is no official PHP version "5.6.40" in the standard PHP release history. The official versions were 5.6.39 and then 5.6.40 (Release Date: Jan 10, 2019). However, given the high likelihood of a typo, this post covers PHP 5.6.40 (the last official security release of the 5.6 branch) and also addresses the possibility you meant the 5.6.4.0 alpha build or a general search for CVE links.
: Tiny cracks in how the server handled data, potentially allowing an attacker to crash the system.
If your server runs a version prior to 5.6.40, to these seven security holes with a combined CVSS v3 base score of 9.8 (Critical) . If you arrived here looking for , you
By following these guidelines, you can help mitigate the vulnerabilities in PHP 5.6.40 and keep your server and applications secure.
As of March 2026, only four PHP versions are actively supported: 8.2, 8.3, 8.4, and 8.5. Everything from PHP 8.1 and below is end-
Flaws in the xmlrpc_decode function could allow a remote attacker to cause a system compromise or read memory outside of allocated areas via specially crafted requests.
To help tailor this advice, could you share whether you are trying to running PHP 5.6.40 or if you are preparing a migration plan for a legacy application? Share public link Search the NVD CVE Portal using the keyword
The NVD is the gold standard for security professionals. You can search for "PHP 5.6" to see the long history of CVEs (Common Vulnerabilities and Exposures).
Running an EOL interpreter means that any new exploit vectors found in the core codebase will never receive official security updates from the PHP Group upstream. This deep dive explores the core vulnerabilities affecting PHP 5.6.40, their architectural impact, and how to safeguard your systems. Architectural Breakdown of PHP 5.6.40 Flaws
The story of 5.6.40 is a warning: staying on unsupported software is no longer an option . To survive in a modern landscape of code injection and cryptographic failures , Old Faithful's administrators finally realized they had to let go of the past and upgrade to a supported version like PHP 8.x.
After 5.6.40 was released, many critical CVEs were discovered that affect the 5.6 branch but were for 5.6.x. Examples include: