While 5.6.40 itself was a security update, the environment it lives in is fraught with risks:
A remote code execution (RCE) vulnerability that affects PHP running on Windows in CGI configurations. Attackers can bypass previous protections to execute arbitrary commands. Buffer Overflows & Underflows: CVE-2016-10166: An integer underflow in the gd_interpolation.c CVE-2019-6977: A heap-based buffer overflow in gdImageColorMatch Memory Corruption: CVE-2019-9020: A heap-based buffer over-read in xmlrpc_decode that can lead to system compromise. CVE-2019-9021:
Virtual patching is a temporary band-aid. The only permanent solution to PHP 5.6.40 vulnerabilities is migrating to a supported version, such as PHP 8.2 or PHP 8.3.
Many vulnerabilities discovered in the PHP 5.x engine since 2019 remain unpatched in 5.6.40, including potential Remote Code Execution (RCE) and Denial of Service (DoS) vectors. Vulnerability Database Resources php version 5640 vulnerabilities link
As of 2026, running PHP 5.6.40 poses extreme risks to production environments: PHP Requirements - Knowledgebase - The Events Calendar
I see you're looking for information on PHP version 5.6.40 vulnerabilities. Here's what I found:
PHP 5.6.40 was released on January 10, 2019. It marked the absolute end-of-life (EOL) for the PHP 5.6 release cycle. No official security patches or updates have been issued for this version by the PHP development team since that date. While 5
As of 2026, relying on —the final release of the PHP 5 series launched in January 2019—is a critical security risk. Although it was the last stable version of its era, PHP 5.6 has been unsupported for years, making any installation a prime target for modern cyberattacks. This article breaks down the vulnerabilities, the risks of inaction, and the imperative steps to migrate to a supported version. The Security Reality of PHP 5.6.40
By following these guidelines, you can help mitigate the vulnerabilities in PHP 5.6.40 and keep your server and applications secure.
Modern database drivers, encryption libraries, and framework dependencies (like Laravel or Symfony) no longer support PHP 5.x. Step-by-Step Mitigation Strategy CVE-2019-9021: Virtual patching is a temporary band-aid
Since PHP 5.6 is end-of-life (EOL), new CVEs are not fixed, leaving your site exposed to new, public exploit methods.
Here is the official migration link from PHP.net: