If you are asking about , you are looking at the final, now obsolete release of PHP 5.6 from January 10, 2019. If "5640" refers to a version string like 5.6.4.0 (an old alpha), that version has even more unpatched flaws. This post assumes the former, as it is the more common legacy system reference.
Since PHP 5.6 is end-of-life (EOL), new CVEs are not fixed, leaving your site exposed to new, public exploit methods.
This link provides JSON and XML feeds, official CVSS scores, and impact metrics. php version 5640 vulnerabilities link
: Functions handling image processing ( GD library ), file parsing ( EXIF data ), or string manipulation frequently suffer from boundary-checking flaws.
Once testing is complete, apply the changes to your live site. If you are asking about , you are
Never update a live production site without testing first. Need Help Checking Your PHP Version?
PHP 5.6.40
: PHP 5.6.40 reached the end of its security support on December 31, 2018. Any vulnerabilities discovered after this date remain unpatched by the official PHP team. Vulnerability Statistics
: Addressed flaws that unauthenticated, remote attackers could exploit to compromise systems entirely. Post-Release Risks (EOL Status) Since PHP 5