Microsoft is warning that the original Secure Boot certificates used in Windows 8 and later versions will expire in June and October 2026. These certificates verify PC bootloaders to prevent unverified software from loading during startup. While most modern systems have already received updates through Windows Update, older PCs that miss the deadline could face security and compatibility issues.

Secure Boot has been a formal system requirement for Windows 11 installations since 2021, though it was optional for earlier versions. The certificate expiration isn't new information—Microsoft and PC manufacturers have been preparing for this transition for months. However, systems that don't receive the updated certificates before the deadline will enter a "degraded security state" that limits their ability to install future boot-level protections and may cause compatibility problems with newer operating systems and firmware.

For most users, the transition should be seamless if their PC is running supported Windows versions with Secure Boot enabled. Microsoft is relying on Windows Update to deliver the new certificates to older systems, while newer PCs may have them baked into UEFI firmware. Users can verify their status by checking the active certificate in their system's NVRAM using PowerShell commands. PCs with full or fragmented NVRAM or buggy firmware may encounter deployment issues.