Microsoft Fixes Windows 11 Update Error 0x800f0922: How to Resolve the 35% Rollback Bug

If your PC is throwing the Windows 11 update error 0x800f0922 and rolling back at 35% completion, Microsoft has officially identified the culprit. The frustrating bug is caused by a full EFI System Partition (ESP), but a newly released patch ensures you won't need to manually resize your drives to get your system up to date.

The issue first gained widespread attention following the May 12, 2026, Patch Tuesday release. Microsoft rolled out the mandatory KB5089549 update for Windows 11 versions 25H2, 24H2, and older, introducing features like Xbox mode for desktop. However, many users found their devices stuck at 35-36% completion during the reboot phase, ultimately resulting in an "Undoing changes" screen.

The ESP is a critical FAT32-formatted partition that stores the Windows Boot Manager. It is hidden in the File Explorer (File Explorer) and typically occupies around 256MB. However, if OEM firmware updates consume this space and leave 10MB or less available, Windows updates will fail.

You can verify your available ESP storage by running the following command in PowerShell:

Get-Partition | Where-Object GptType -eq '{c12a7328-f81f-11d2-ba4b-00a0c93ec93b}' | Get-Volume | Format-List Size, SizeRemaining

If your system is affected, the Windows Update history (Windows Update history) page will log the 0x800f0922 error. Additionally, advanced users checking the Event Viewer (Event Viewer) at C:\Windows\Logs\CBS\CBS.log will see the failure explicitly flagged as insufficient free space.

Microsoft has confirmed that you do not need to manually expand your ESP. Instead, follow these steps to resolve the issue:

1. Open your system settings and navigate to the Windows Update page.
2. Look for the optional update labeled KB5089573 (Build 26200.8524 or newer), released on May 26, 2026.
3. Download and install the patch to bypass the ESP storage limitation.

If you prefer not to install optional previews, Microsoft noted in an updated document that the fix will be bundled automatically into the next mandatory Patch Tuesday release on June 9, 2026.

The root cause of this update failure highlights a growing friction point in modern PC architecture. Hardware manufacturers (OEMs) are increasingly pushing massive BIOS updates to support complex graphical interfaces and advanced security modules. This trend places immense pressure on the EFI System Partition, which was originally designed years ago to hold tiny bootloaders.

As these firmware files accumulate, it was only a matter of time before standard OS updates began to choke. Microsoft's decision to patch the Windows Update mechanism to gracefully handle this bottleneck is a critical quality-of-life improvement. By bypassing the need for everyday users to manually resize disk partitions - a highly risky process that can lead to catastrophic boot failures - Microsoft is making Windows 11 significantly more resilient to hardware-level constraints.