PHP version 5.6.40 was released on January 10, 2019, as the final security release for the PHP 5.6 branch. While it addressed several critical security bugs at the time, it reached its official End of Life (EOL) on December 31, 2018, meaning it has not received official security updates or bug fixes for over seven years. Key Vulnerabilities in PHP 5.6.40
Although 5.6.40 was a "security release," it remains vulnerable to numerous exploits discovered after its EOL. Because the PHP project no longer maintains this branch, any vulnerability found since 2019 remains unpatched in official builds.
Heap-Based Buffer Over-reads (CVE-2019-9023): This critical vulnerability occurs in mbstring regular expression functions when they are supplied with invalid multibyte data. It can allow a remote attacker to compromise the target system.
PHAR Reading Issues (CVE-2019-9021): A heap-based buffer over-read in the PHAR extension may allow attackers to read memory past actual data while parsing filenames. php version 5640 vulnerabilities link
Integer Underflow (CVE-2016-10166): An issue in the _gdContributionsAlloc function in gd_interpolation.c can have unspecified impacts via unauthenticated remote attacks.
Exposed phpinfo() Page: While not a vulnerability in the code itself, many legacy 5.6.40 setups leave the phpinfo() page public, which discloses sensitive server information that aids in formulating Remote Code Execution (RCE) or Local File Inclusion (LFI) attacks. Security Risk Summary
Using PHP 5.6.40 in 2026 is considered high-risk. Automated scanners frequently identify hundreds of known vulnerabilities in environments running this version. Snyk - Vulnerability report for Docker php:5.6.40-apache PHP version 5
While searching for "php version 5640 vulnerabilities link" , many sysadmins expect to find a single official PHP.net advisory. Here is the truth: PHP.net does not host a "Vulnerabilities for 5.6.40" page.
Instead, they provide a critical link:
Direct link to the PHP 5.6.40 EOL announcement: https://www.php.net/eol.php Search results for PHP 5
This page states unequivocally that security fixes for PHP 5.6 ceased on December 31, 2018. Version 5.6.40 was released after EOL. This means that any vulnerability discovered after January 2019 (including most CVEs listed above) is permanently unfixed in 5.6.40.
There is no permanent security fix for PHP 5.6.40 other than upgrading.
The jump from PHP 5.6 to PHP 7.x (and now PHP 8.x) is significant. PHP 7.0 was a major rewrite that offered massive performance gains (2x-3x faster) and strict typing, but it broke backward compatibility.
Migration Path: