EFI partition Archives

Winsage

May 20, 2026

Microsoft confirms Windows 11’s May 2026 update is failing to install with error 0x800f0922 and outlines a mitigation for affected PCs

Microsoft has acknowledged installation issues with the May 2026 Security Update for Windows 11, specifically error code 0x800f0922, affecting devices on versions 24H2 and 25H2 after installing update (KB5089549) released on May 12. The failures occur during the reboot phase, often around 35 percent, primarily on devices with 10MB or less free space in the EFI System Partition (ESP). For consumer and unmanaged business devices, Microsoft has implemented a Known Issue Rollback (KIR), and restarting the computer may resolve the issue. For managed devices, network administrators must manually deploy a Group Policy workaround. Microsoft suggests modifying a Registry value to decrease reserved padding in the EFI partition as a potential fix, along with restarting the computer and checking for updates. A permanent solution is planned for a future Windows update.

Winsage

May 19, 2026

Yet Another Windows Update Done In By The EFI System Partition

The EFI System Partition (ESP) is an important part of modern computing that users are generally advised to avoid tampering with. Insufficient space on the EFI partition can lead to ambiguous error messages during updates, particularly with Microsoft’s security updates. The EFI partition is typically mapped to drive Y:, but may also be assigned to Z: or other letters. In some cases, such as transitioning from Windows 10 to Windows 11, users may need to access the EFI partition, where one solution involves removing TrueType Font (TTF) files under EFIMicrosoftBootFonts. However, caution is advised when handling the EFI partition, as mistakes can prevent the operating system from booting.

Winsage

May 17, 2026

Microsoft confirms Windows 11 KB5089549 issues due to low storage, says it’s rolling out an emergency patch to fix install errors

Microsoft has acknowledged an issue with the installation of Windows 11’s May 2026 Update (KB5089549), which has been encountering errors such as 0x800f0922, 0x80240069, and 0x80240031. An emergency server-side update is being implemented to resolve these installation hurdles. The KB5089549 update is mandatory and intended to install automatically on compatible PCs, but some users have reported difficulties, including installation stalling around 35-36%, leading to a rollback with a message stating, “something didn’t go as planned. Undoing changes.” Investigations reveal that installation failures are particularly affecting devices with limited EFI partition space, with error code 0x800f0922 indicating insufficient free space and potential conflicts with third-party files. The EFI System Partition (ESP) typically occupies no more than 100MB and can become congested due to leftover files, causing installation failures when available space is low. Users with less than 10MB of free EFI storage may face additional complications. A PowerShell command can be used to check EFI storage status. Microsoft has advised users to consider increasing the size of the ESP by modifying the Windows Registry, although the recent server-side update may have already addressed the issue. The Known Issue Rollback (KIR) has been implemented, automatically propagating the resolution to devices. Users are encouraged to restart their devices to expedite the application of the fix, and there are no additional bugs reported.