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).
Outdated libraries and extensions (e.g., mysql_connect ) used in PHP 5.6 are often insecure and incompatible with modern database technologies. Key Vulnerability Areas
Even the version is not safe if you use an unpatched FPM—the vulnerability was fixed in Debian via 5.6.40+dfsg-0+deb8u7 and later in Amazon Linux in ALAS‑2019‑1315.
Released on January 10, 2019, PHP 5.6.40 marked the absolute end-of-life (EOL) for the entire PHP 5 release branch. Because the PHP community stopped issuing security patches for this version years ago, legacy web applications remaining on this release remain fully exposed to automated botnets, data breaches, and ransomware.
: Websites like PHP.net and others dedicated to PHP security provide detailed advisories on vulnerabilities, patches, and best practices to mitigate risks. php version 5640 vulnerabilities link
The multibyte string component ( mbstring ) contains multiple heap buffer over-read flaws within its regex processing functions. Functions handling multibyte tokenizing ( fetch_token ) or structural compilation ( compile_string_node ) fail to check string lengths properly. An attacker submitting a crafted multibyte string sequence can cause the PHP interpreter to leak system memory structures past allocated boundaries. 3. PHAR Extension Directory Traversals (CVE-2019-9021)
As Cloudways reports, the stable landscape has evolved to . Staying on 5.6.40 means missing out on:
An unauthenticated attacker can upload a malformed image payload to trigger application crashes or execute shell commands. A full profile is provided in the Tenable Nessus PHP 5.6.40 Plugin . 📊 Summary of Vulnerabilities Impacting PHP 5.6.40 PHP - endoflife.date
: Review the PHP 5 ChangeLog to see the exact security bugs closed in the final 5.6.40 release, illustrating what remains open if you run any version lower than 5.6.40. Version 5
: The official PHP website often has a section on security where you can find information on known vulnerabilities, how to report them, and advisories.
Because PHP 5.6.40 has been EOL for years, it has accumulated a backlog of known vulnerabilities that will never be fixed. While PHP 5.6.40 patched issues present in earlier 5.6 versions (like 5.6.30), it is vulnerable to classes of bugs discovered after January 2019.
Use tools to scan your codebase for deprecated functions.
This application-level vulnerability is common in outdated applications, allowing attackers to manipulate serialized objects, leading to RCE or data corruption. Released on January 10, 2019, PHP 5
Websites still running PHP 5.6.40 face a broad attack surface. Because security researchers continuously audit old codebases, multiple unpatched vulnerabilities affect infrastructure utilizing this version. 1. Memory Corruption and Use-After-Free
For a comprehensive list of CVEs (Common Vulnerabilities and Exposures), you can review the PHP News Archive or the National Vulnerability Database. Why 5.6.40 is No Longer Safe
There is no single “master link” labeled "5640." Instead, you must look at the aggregate of Common Vulnerabilities and Exposures (CVEs) that affect version 5.6.40.