As of 2026, running PHP 5.6.40 poses extreme risks to production environments: PHP Requirements - Knowledgebase - The Events Calendar
These vulnerabilities, and others like them, were patched in later versions of PHP. However, since PHP 5.6.40 is no longer supported, websites using this version are left to fend for themselves, exposed to these known security risks. php version 5640 vulnerabilities link
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). As of 2026, running PHP 5
| CVE ID | Description | CVSS | |--------|-------------|------| | | Remote code execution via env request variable (PHP-FPM) – unpatched in 5.6.40 | 9.8 (Critical) | | CVE-2019-9641 | Buffer overflow in php_url_parse_ex – DoS/RCE | 7.5 (High) | | CVE-2019-9020 | XML parsing vulnerability in libxml2 affecting PHP | 7.5 | | CVE-2018-20783 | Buffer over-read in php_escape_html_entities | 7.5 | | CVE-2016-10712 | Use-after-free in stream_get_filters | 7.5 | | CVE ID | Description | CVSS |
: Overwhelming the server until it could no longer serve its users.
For those who simply need to know the worst offenders linked to version "5640," here are the top CVEs that remain unpatched in 5.6.40.
If you have stumbled upon the search term , you are likely dealing with a legacy system running PHP 5.6.40—the very last official release of the PHP 5.x series, published on January 10, 2019.
