Fixing NVIDIA Driver "Unavailable Key" Error After a Windows Update

Recently, I ran into an issue with the NVIDIA driver after an unexpected Windows update. The update reordered the BIOS boot entries, and when I subsequently booted into Fedora 43, the NVIDIA kernel module failed to load with an “unavailable key” error.

I have been using the proprietary NVIDIA driver with Secure Boot enabled for a long time without any issues, so this behavior was unexpected. However, after researching the problem, I discovered that the Secure Boot signing key previously enrolled on my system was no longer recognized, likely due to changes triggered by the Windows update or the altered boot configuration.

After some investigation, I was able to resolve the issue by manually importing the NVIDIA module signing key into the system’s Machine Owner Key (MOK) database. Fedora provides official documentation for this process under How to / Secure Boot. Even if you are not using Fedora, this guide can serve as a useful reference.

In short, the fix was:

1. Import the module signing key into the system.
2. Enroll the key via MOK during the next boot.
3. Reboot and verify that the NVIDIA driver loads correctly under Secure Boot.

Once the key was properly enrolled, the NVIDIA driver loaded as expected, and Secure Boot remained enabled.

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