The PHP development team has verified several vulnerabilities in PHP version 5.6.40, which are listed below:

PHP version 5.6.40 was the final "security-only" release for the PHP 5.6 branch. As of April 2026, this version has been unsupported for over seven years. Any vulnerabilities discovered after January 2019 remain unpatched by the official PHP development team, posing a severe risk to data integrity and server security. Key Verified Vulnerabilities

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PHP Version 5.6.40: Verified Vulnerabilities and the Risks of Outdated Code

Memory corruption vulnerabilities allow attackers to interfere with a program's execution, often leading to a crash (Denial of Service) or complete system takeover.

Outdated versions are highly susceptible to RCE through unpatched bugs in core functions or extensions like Unpatched Dependency Chains:

Specially crafted files (like a corrupted JPEG image parsed via EXIF) can trigger a buffer overflow.

: An integer underflow in the _gdContributionsAlloc function allows remote attackers to cause unspecified impact via specially crafted image data.

Version 5.6.40 was designed to be the most stable version of PHP 5, but its age now makes it a prime target for automated scanning tools. PHP 5.6.40 Release Announcement

Because many legacy systems still run PHP 5.6, it is a high-priority target for automated exploit kits and unauthenticated SQL injection attacks.

The absolute best defense is migrating to a actively supported version of PHP (such as PHP 8.2 or 8.3).

High to Critical.

Host takeover allowing attackers to encrypt server files for financial extortion.

Beyond code execution, PHP 5.6.40 is susceptible to numerous denial-of-service (DoS) and information disclosure attacks.

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