End of servicing is the point when a software release stops receiving regular updates and security fixes. The product may still run, but its vendor no longer patches newly discovered vulnerabilities, which steadily increases risk over time.
In cyber security, this matters because unpatched software is a common target for attackers. Once support ends, any weakness found in that version can remain open unless an organization upgrades or adds compensating controls such as segmentation, tighter monitoring, restricted access, or isolation. Defenders track servicing deadlines to inventory affected systems, plan migrations, and retire legacy platforms before they become easy footholds in an attack path.