For government-grade tracking, use the NVD:
PHP Vulnerabilities: Assessment, Prevention, and Mitigation - Zend php version 5640 vulnerabilities link
: Systems running 5.6.4x or earlier are often flagged for multiple vulnerabilities including: While PHP 5
PHP 5.6.40 is an older version of PHP, and as such, it has some known vulnerabilities. According to the PHP security team, PHP 5.6.40 has several fixed vulnerabilities. Here are a few: For government-grade tracking
Here are the authoritative links to search for PHP 5.6.40 vulnerabilities:
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.
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.