Linux and Secure Boot certificate expiration

A Microsoft Secure Boot certificate used to sign Linux's shim bootloader is expiring in September 2025, after which Linux installation media will no longer boot on systems without an updated Microsoft key from 2023. Many systems lack this newer key and will require firmware updates from hardware vendors to resolve the issue, though existing Linux installations should continue to work. The Linux community is preparing mitigation strategies through tools like fwupd and the Linux Vendor Firmware Service, though users may need to take action to update their systems.