virtualbox.org

I just updated VBox from 6.1.22 to latest 6.1.26 on my macOS 11.5.1.

Now I cannot start start VM Windows 10 and get error message: Kernel driver not installed (rc=-1908).

Any advice what to do?

I suggest you look at the sticky topics at the top of this forum.

You need to keep the Apple System Preferences > Security and Privacy open when installing/upgrading VirtualBox to see a 'warning message' and then input the system password and 'Allow' the upgrade or the kernel drivers don't get properly installed.

Blame Apple for the obscurity of this procedure.

Thanks, works fine.

BTW The top post on Issues with Big Sur is about 1.5 months old latest post and answer not as clear as I got here.

Glad it worked for you.

As you will have seen from the previous thread mentioned, some users have problems with the 'Warning Massage not appearing, but I suspect that's caused by multiple failed installations "blocking-up" MacOS with the partially installed software. Life would be so much easier if Apple had programmed a Desktop 'pop-pup' advisory warning about the user action needed if a software installation needs permission to interact/integrate directly with MacOS.

On macOS Mojave Beta:

1. Download the DMG
2. Open System Setting / Security and Privacy
3. If the lock at the bottom is closed: Enter password and open the lock
4. Now return to the DMG, mount it and click 'Install'.
5. DO NOT delete the DMG.

Worked for me until the next reboot. After the reboot continue at No. 2.
That is why you need No. 5.