This week, Windows 10/11 users who installed the August 2024 security patch reported an issue where they couldn’t boot into Linux in a dual-boot system. Microsoft has confirmed this problem.
The security patch was intended to fix a vulnerability in GRUB, a widely used boot selection system in the Linux world. This vulnerability allowed hackers to bypass secure boot, with a severity rating of 8.6/10 and being known for two years.
Microsoft’s patch, released two years late, will install Secure Boot Advanced Targeting (SBAT), a mechanism that revokes boot software rights if a risk is detected. However, it appears the patch is designed for hardware booting exclusively to Windows, causing issues for dual-boot hardware displaying “Verifying shim SBAT data failed: Security Policy Violation.”
Image by paku1234 from Reddit r/linux4noobs
Microsoft has acknowledged the problem and is investigating with Linux partners. Their current recommendation is for dual-boot systems to avoid installing the August 2024 patch or, if already installed, refrain from rebooting to ensure the patch takes effect.
For users experiencing the issue, temporarily disabling Secure Boot and deleting the SBAT policy in Linux will allow them to re-enable Secure Boot. Instructions are available from Ars Technica and Neowin.
TLDR: Windows patch causes booting issue for Linux dual-boot systems, Microsoft acknowledges problem and advises temporary solutions for affected users.
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