Encountered Vagrant Up error on MacOs Big Sur Upgrade

I had the same issue after updating to Big Sur. I downloaded the latest versions of Vagrant, Virtualbox and VirtualBox Extension Pack. Actually, I don't know if installing the Extension Pack was necessary.

And in the system preferences of MacOS, in Privacy and Security, I had to approve the update from Oracle.

After these steps, I was able to 'vagrant up' again.

Updating VirtualBox to 6.1.16 did it for me. I did not update Vagrant

Updating VirtualBox to 6.1.16 did it for me, not working with 6.0.24. Also reinstalled Vagrant but not sure if necessary.

The allow oracle button in privacy and security never showed up in my settings. Eventually I got it working by booting in recovery mode and running the command

csrutil clear

After that I was able to allow oracle in security and privacy.