for this version, leaving it permanently exposed to any vulnerabilities discovered over the last several years. Critical Vulnerabilities in PHP 5.6.40
Utilize curated, paid repositories that offer custom security patches for legacy stacks. Step 3: Disable Vulnerable Functions
Running an EOL language version means that any security flaw discovered after January 2019 remains permanently unpatched in the core software. Attackers actively scan the internet for signatures of old PHP versions to deploy automated exploit toolkits. Core Risks
function, potentially allowing an unauthenticated remote attacker to compromise the system. Risks of Using PHP 5.6.40 in 2026
Upgrading to a newer PHP version is essential for maintaining the security and integrity of your website. Some of the benefits of upgrading include: php version 5640 vulnerabilities link
Functions like gdImageColorMatch suffer from heap-based buffer overflows due to incorrect calculations of allocated buffer sizes. Additionally, an integer underflow condition exists in _gdContributionsAlloc .
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.
Attackers can exploit flaws in older PHP versions to execute arbitrary code on the server, gaining full control over the website and underlying infrastructure.
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- for this version, leaving it permanently exposed to
and no longer receives official security updates from the PHP Group. Core Vulnerabilities and Security Status Official Support Status
Flaws reside in phar_detect_phar_fname_ext within ext/phar/phar.c . When PHP attempts to parse a malformed PHAR filename, it fails to evaluate bounds accurately.
Since the source code for PHP is open, security researchers and malicious actors know exactly which vulnerabilities exist in 5.6.40. It is a sitting duck.
Because PHP 5.6.40 is end-of-life (EOL), it remains vulnerable to multiple critical issues disclosed since its final release, including: CVE-2024-4577 (Critical - CVSS 9.8): Attackers actively scan the internet for signatures of
While the PHP team stopped listing specific 5.6 bugs years ago, numerous high-severity vulnerabilities remain unpatched:
Because this version is End-of-Life (EOL), any vulnerabilities discovered after its final release remain unpatched by the official PHP development team. Core Vulnerabilities in PHP 5.6.40
Version 5.6.40 was released in January 2019, and it has many known security issues because it reached on December 31, 2018 (no more security patches).
Staying on PHP 5.6.40 is a high-risk gamble with your application's security. While LTS vendors provide some patches, these are only stopgaps. The most responsible and secure action is to plan and execute a migration to a supported PHP version. The information and links provided here serve as a roadmap to navigate this critical upgrade. A modern, secure PHP environment is not just an option—it's a necessity.