Microsoft quietly fixes the dual-boat bug of last summer

In silence, Microsoft has finally fixed a dual-boat bug, which has repeatedly pose problems with a number of users since last year. There was a workaround that was relatively complicated.

Small problem, big effect

It started in August 2024. At that time, a safety update from Microsoft caused significant problems for users who operate Windows 11 together with a Linux system. Numerous popular Linux distributions such as Ubuntu, Debian, Linux Mint, Zorin OS and Puppy Linux were affected. After installing the update at the time with the identification KB5041585, the starting process of Linux operating systems failed. Instead, an error message appeared with reference to a “Security Policy Violation” when checking the so-called SBAT data.

SBAT stands for “Secure Boot Advanced Targeting” and is a safety function that is supposed to block outdated or unsafe boot loaders. The system uses a database with blocked UEFI components. The function was originally intended to rule out potentially dangerous boot loaders. However, the SBAT test was also incorrectly activated for systems that ran with Linux in dual-boat operation-a scenario that should actually be excluded from the new safety regulation.

Fixed in the May Update

Microsoft reacted a few days after the problem became known with a complex workaround that required changes to the group guidelines and the Windows registry. For many users, however, this solution was too technical and not very user -friendly. Now Microsoft has also delivered an error correction as part of the May Update, which under the identification KB5058405 is listed. The correction ensures that the SBAT examination correctly recognizes in the future whether a system will be operated in dual-boat mode and, in such cases, does not use the restrictive safety measure.