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Windows 11 Commercial Boot Failure Bug Resolved in February 2026 Update
Sunday, February 15, 2026
What
A bug in Windows 11 caused commercial physical devices to become unbootable, displaying an "UNMOUNTABLE_BOOT_VOLUME" error, after installing recent security updates. This matters because it led to critical system downtime for affected enterprises, requiring manual recovery.
Where
Limited number of commercial Windows 11 devices (versions 25H2 and 24H2) globally.
When
Issue linked to failed December 2025 updates, manifesting after January 13, 2026 updates. Fix released February 10, 2026.
Key Factors
- •The boot failures were triggered by an improper system state resulting from a failed December 2025 security update installation rollback.
- •Affected systems, specifically physical commercial Windows 11 devices running versions 25H2 and 24H2, would then fail to boot after installing subsequent updates.
- •Microsoft provided an initial preventative resolution in KB5074105 and a full resolution in the February 2026 Patch Tuesday update KB5077181.
Takeaways
- →Enterprise customers should ensure all Windows 11 25H2/24H2 systems are updated with KB5077181 or later to prevent this boot issue.
- →Organizations with unbootable devices must contact Microsoft Support for Business for specific recovery guidance.
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