Windows 11 KB5077181 Fixes Boot Failures Linked to Failed Updates

Why It Matters

Boot reliability is critical for business continuity; fixing this flaw prevents costly downtime and restores confidence in Windows 11’s update pipeline.

Key Takeaways

• KB5077181 resolves UNMOUNTABLE_BOOT_VOLUME error on Windows 11.
• Issue impacted commercial devices running 25H2 and 24H2 builds.
• Root cause was failed December 2025 security update installation.
• January 13, 2026 KB5074109 triggered boot failures for some systems.
• Enterprise customers may need Microsoft Support for remediation.

Pulse Analysis

The recent Windows 11 boot issue underscores how a single failed update can cascade into system‑wide failures, especially in enterprise environments where uptime is non‑negotiable. Historically, Microsoft’s Patch Tuesday cadence has balanced security with stability, yet the December 2025 update slipped through quality checks, leaving devices in an "improper state" that later patches could not resolve. This incident highlights the importance of rigorous regression testing for cumulative updates, particularly for core components like the boot manager, which affect every Windows installation.

Affected machines were limited to physical devices running the 25H2 and 24H2 channels, a segment that includes many corporate desktops and laptops. The error manifested as an "UNMOUNTABLE_BOOT_VOLUME" message followed by a black screen, forcing IT teams into manual recovery procedures. Because the problem originated from a failed December 2025 installation, subsequent updates—including the January 13, 2026 KB5074109 security patch—could not be applied, effectively locking the system out of the update ecosystem. Enterprises that rely on automated deployment tools faced additional complexity, needing to isolate and quarantine the faulty devices while maintaining security compliance.

Microsoft’s response arrived in two stages: an optional preview (KB5074105) in late January that halted further spread, and the definitive fix (KB5077181) released on February 10, 2026. The latter not only restores boot functionality but also patches the underlying installer logic to prevent recurrence. Organizations with lingering issues are urged to engage Microsoft Support for Business, ensuring a clean remediation path. The episode serves as a reminder that even mature operating systems require vigilant update management and that transparent communication from vendors remains essential for enterprise risk mitigation.

Windows 11 KB5077181 fixes boot failures linked to failed updates

July 18 2024

Microsoft says it has resolved a Windows 11 bug that caused some commercial systems to fail to boot with an “UNMOUNTABLE_BOOT_VOLUME” error after installing recent security updates. The fix was delivered in the February 2026 Patch Tuesday update.

The boot issue, which Microsoft previously investigated and linked to failed December 2025 updates, affected a limited number of commercial Windows 11 devices running versions 25H2 and 24H2.

According to a private enterprise advisory seen by Susan Bradley of Ask Woody, the issue has now been marked as fully resolved in the Windows 11 KB5077181 security update released on February 10, 2026.

Microsoft says impacted devices suffered boot failures after installing the January 13, 2026 security update KB5074109 (or later updates), displaying a black screen and the message:

“Your device ran into a problem and needs a restart. You can restart.”

At that point, impacted systems were unable to boot and required manual recovery to restore functionality.

Microsoft previously confirmed the issue was caused by the failed installation of the December 2025 security update, leaving devices in an improper state after the installation rolled back. Attempting to install future Windows updates on devices with this “improper state” could cause the system to become unbootable.

Microsoft said the issue affected only physical devices running Windows 11 25H2 and 24H2, and did not receive reports of it affecting home users or virtual machines.

Fix delivered in February Patch Tuesday update

Microsoft says it previously released an initial resolution in the optional non‑security preview update KB5074105 on January 29, 2026, which helped prevent additional systems from becoming affected by the bug.

The company now says the issue is fully resolved in the Windows 11 KB5077181 update released during the February 2026 Patch Tuesday and later updates.

“This issue is fully resolved in the Windows security update released on February 10, 2026 (the Resolved KBs listed above), and later updates,” reads Microsoft’s advisory.

Unfortunately, devices that became unbootable before the fix was released may still require additional remediation. Microsoft advises enterprise customers whose devices remain affected to contact Microsoft Support for Business for assistance restoring system stability.

It is unclear why Microsoft did not share this advisory publicly, as it does for other known Windows issues.