Microsoft has confirmed that August security updates for supported versions of Windows mistakenly applied Secure Boot Advanced Targeting (SBAT) settings to some dual-boot Windows and Linux systems. Because of this, users might encounter an error when trying to run Linux on their device.
Microsoft has also published instructions that will fix the problem.:
Disable secure boot in the BIOS.
Boot into Linux and open a terminal.
Delete the SBA policy using the command: sudo mokutil –set-sbat-policy delete You will need the password of the ROOT user.
Reboot and re-enable Secure Boot in the BIOS.
Boot into Windows, run the command prompt as an administrator, and run the following command:
reg add HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\SecureBoot\SBAT /v OptOut /d 1 /t REG_DWORD
This command will prevent the new SBAT policy from being applied again.
The company says it is working with Linux partners to resolve the issue as soon as possible.