Microsoft Resolves Windows 11 Update Failure Issue Due to Limited EFI System Partition Space

Microsoft has verified that certain PCs with inadequate EFI System Partition (ESP) space were unable to complete the May 2026 cumulative update installation. This issue, which impacted a specific group of users, has been addressed with an optional update (KB5089573). Installing this update should prevent further update failures.

May 2026 Patch Tuesday (KB5089549) and Associated Problems

On May 12, 2026, Microsoft rolled out the Patch Tuesday update (KB5089549) for Windows 11 versions 25H2, 24H2, and earlier builds. This update introduced various features, including an Xbox mode for desktop and fixes for explorer.exe-related issues. However, many users reported failures to install the update, receiving the error code 0x800f0922.

This error code commonly occurs due to insufficient free space in the EFI System Partition (ESP). While the update installed successfully on some systems, others encountered problems caused by the limited storage capacity of this partition.

Understanding the EFI System Partition (ESP)

The ESP is a vital partition required by all Windows installations, regardless of the OEM or version. It stores essential boot files, including the Windows Boot Manager. Without the ESP, a PC cannot boot properly.

Windows automatically generates the ESP during installation, and it remains hidden in File Explorer due to its importance. Usually, this partition only requires a small amount of space, such as 256MB, with the majority of installations retaining over 100MB of free space. However, insufficient space in the ESP can lead to Windows update failures.

Checking ESP Storage

Users can check the available storage in their ESP using specific commands. Microsoft clarified that the May 2026 update introduced changes that caused issues for systems with limited ESP space. This resulted in updates failing at around 35–36% installation progress, followed by a rollback attempt and the error message: "Something didn’t go as planned. Undoing changes."

Why Does ESP Run Out of Space?

Under normal conditions, Windows does not continuously consume ESP storage. This partition typically maintains a disk footprint of less than 100MB, with 60–80% free space remaining. However, certain updates, such as BIOS updates released by OEMs, may increase the size of the ESP, potentially leading to space shortages.

If the ESP has less than 10MB of free space, Windows updates may fail to install. Although users can technically expand the ESP size manually, this is a complex process best left to experienced users. Thankfully, Microsoft has implemented a solution that eliminates the need for manual intervention.

Microsoft's Solution for the ESP Issue

In an updated support document, Microsoft confirmed that the optional update (KB5089573, Build 26200.8524 or later) resolves the root cause of this issue. Installing this update ensures that limited ESP space will no longer hinder future Windows updates.

Microsoft recommends installing the optional update if you encountered failures with previous updates, such as the May 2026 Patch Tuesday update. According to the company, "This issue was resolved by Windows updates released May 26, 2026 (KB5089573), and later." Additionally, all future updates will incorporate this fix, so users who skip the optional update will still receive the resolution in the June 2026 Patch Tuesday update, scheduled for June 9, 2026.

Conclusion

The optional update KB5089573 offers a reliable solution for users facing Windows update issues due to insufficient ESP space. Microsoft assures users that future updates will also include this fix, simplifying the update experience and removing the need for manual adjustments to critical partitions.