Operating system end-of-life is the most critical lifecycle event in any infrastructure environment. When an OS loses support, every application running on it inherits the same unpatched vulnerability exposure — regardless of whether the application itself is still supported.
An operating system past its end-of-life date stops receiving security patches. This means every CVE disclosed after that date — affecting the kernel, system libraries, networking stack, or any OS component — accumulates indefinitely with no remediation path. The blast radius extends to every application running on that system.
Windows 10 reached EOL in October 2025. Millions of enterprise endpoints are still running it. CentOS 7 reached EOL in June 2024 — a massive installed base of Linux servers with no upstream patches. These are not edge cases. They are the most common security exposure in enterprise environments today.
Compensating controls — network segmentation, enhanced monitoring, access restriction — can reduce exposure but cannot eliminate it. Migration to a supported OS version is the only permanent remediation.