Windows 11 KB5094126 EFI Partition Error 0x800f0922 June 2026 Fix

What is the KB5094126 EFI Partition 0x800f0922 Issue?

The June 10, 2026 Patch Tuesday cumulative update KB5094126 (Build 26100.4995 for 24H2 / 26200.2410 for 25H2) ships a new servicing-stack bootloader payload that must be written to the EFI System Partition (ESP) at install time. When the ESP has less than ~12 MB free, the post-reboot servicing phase fails at 71%–94% with error 0x800f0922 (CBS_E_INSTALLERS_FAILED) and rolls back. Microsoft confirmed this specific failure mode in the KB5094126 advisory updated June 12, 2026 and shipped a Known Issue Rollback (KIR) for managed environments only — home PCs still need to clear the ESP manually.

This is a different failure than the 0x80073712 WinSxS-corruption rollback covered in our [KB5094126 0x80073712 article](/en/errors/windows-11-kb5094126-june-2026-install-error-0x80073712). The 0x800f0922 variant happens earlier in the staging process and always points to ESP capacity. If your CBS.log shows STATUS_DISK_FULL near the \Device\HarddiskVolume1 reference, you're in the right place.

When does it occur?

• KB5094126 fails at 71%–94% during the post-reboot servicing screen with 0x800f0922
• mountvol Y: /s then Get-Volume -DriveLetter Y shows SizeRemaining below 12 MB
• The PC was originally imaged before 2018 (default 100 MB ESP)
• Dual-boot setup with Linux/macOS occupying additional \EFI\ folders
• OEM systems where Winre.wim was placed inside the ESP rather than a dedicated recovery partition
• After installing KB5089549 or KB5089573 successfully — those updates already shaved the ESP free space

Common causes

• ESP is only 100 MB and cumulative updates have left it under the new 12 MB watermark
• Orphaned bootmgfw.efi.bak and BCD.LOG1/BCD.LOG2 from prior cumulatives
• Duplicate boot fonts in \EFI\Microsoft\Boot\Fonts\ (wgl4_boot.ttf, segoe_slboot.ttf, language packs)
• \EFI\ubuntu\, \EFI\refind\, \EFI\clover\ folders from past dual-boot setups
• Winre.wim (≈500 MB) residing in the ESP on OEM-imaged Dell, HP, Lenovo, Acer machines
• Pre-boot BitLocker authentication binaries left from a removed manage-bde configuration
• Stub \EFI\Boot\bootx64.efi copies from failed feature-update attempts

Step-by-step fixes

1. Identify the ESP and mount it. Open an elevated PowerShell and run:

   mountvol Y: /s
   Get-Volume -DriveLetter Y | Select-Object SizeRemaining, Size

SizeRemaining below 12582912 bytes (12 MB) means KB5094126 will roll back. Browse with dir Y:\EFI\.

1. Delete safe, regeneratable files. Windows will recreate these on next boot:

   Remove-Item "Y:\EFI\Microsoft\Boot\Fonts\*.ttf" -Force
   Remove-Item "Y:\EFI\Microsoft\Boot\*.bak" -Force
   Remove-Item "Y:\EFI\Microsoft\Boot\BCD.LOG*" -Force
   Remove-Item "Y:\EFI\Microsoft\Recovery\BCD.LOG*" -Force -ErrorAction SilentlyContinue
   Get-Volume -DriveLetter Y | Select-Object SizeRemaining

Typically frees 6–15 MB. Re-check SizeRemaining; if you're now above 12 MB, skip to step 7.

1. Remove orphaned third-party bootloader entries. From an elevated prompt, list every UEFI entry with bcdedit /enum firmware. Delete unused ones with bcdedit /delete {guid}, then drop their folders:

   Remove-Item "Y:\EFI\ubuntu" -Recurse -Force -ErrorAction SilentlyContinue
   Remove-Item "Y:\EFI\refind" -Recurse -Force -ErrorAction SilentlyContinue
   Remove-Item "Y:\EFI\clover" -Recurse -Force -ErrorAction SilentlyContinue

Each typically reclaims 2–8 MB. Skip this step if you actively dual-boot.

1. **Move Winre.wim off the ESP.** Run reagentc /info. If the output's Windows RE location references harddisk0\partition1, partition 1 is your ESP and Winre.wim is the elephant in the room. Run:

   reagentc /disable
   robocopy Y:\Recovery\WindowsRE\ C:\Recovery\WindowsRE\ Winre.wim /MOVE
   reagentc /setreimage /path C:\Recovery\WindowsRE
   reagentc /enable

This frees roughly 500 MB instantly.

1. Run the KB5094126 ESP cleanup helper (released June 12, 2026). Microsoft published KB5094126-ESPClean.ps1 via the Update Catalog. Download, then in an elevated PowerShell:

   Set-ExecutionPolicy -Scope Process Bypass -Force
   .\KB5094126-ESPClean.ps1 -Verbose

The script audits the ESP, prints every file it can safely remove, and asks for confirmation before deleting. This is the Microsoft-blessed equivalent of steps 2–3.

1. Resize the ESP with MiniTool Partition Wizard or AOMEI Partition Assistant. If cleanup is not enough, free editions support a shrink-and-extend workflow. Shrink C: by 200 MB → move the unallocated space until adjacent to the ESP → extend the ESP by 200 MB. Image your disk before resizing with Macrium Reflect Free or wbAdmin — a botched resize leaves the PC unbootable until repaired with the Windows 11 install media.

1. Retry KB5094126. Unmount the temporary letter: mountvol Y: /D. Then Settings → Windows Update → Check for updates. KB5094126 should now install past 96% and report Build 26100.4995 (24H2) or 26200.2410 (25H2) when you run winver.

1. **Verify the install with DISM.** DISM /Online /Get-Packages | Select-String "5094126" should now list Package_for_KB5094126~...~26100.4995 (or 26200.2410). If the package is Resolved or Staged but not Installed, reboot once more — the post-install commit sometimes spans two reboots after an ESP cleanup.

If it still doesn't work

If SizeRemaining is above 12 MB but KB5094126 still rolls back with 0x800f0922, the failure has shifted from a capacity problem to a manifest-write problem. Open C:\Windows\Logs\CBS\CBS.log and search for the first 0x800f0922 occurrence — the immediately preceding [CSI] line will name the failing payload (usually boot.sdi, bootmgfw.efi, or a locale .nls file). Take ownership of \EFI\Microsoft\Boot\<that file> with takeown /f and icacls, delete it, then retry. If the failing file is bootmgfw.efi itself, restore it from a clean source: mount the current Windows 11 ISO and copy \sources\install.wim\1\Windows\Boot\EFI\bootmgfw.efi to Y:\EFI\Microsoft\Boot\. For BitLocker-enabled systems, suspend protection first with manage-bde -protectors -disable C: -RebootCount 2, or the firmware will demand the 48-digit recovery key after the ESP write completes. The Microsoft KB5094126 support page (microsoft.com/help/5094126) lists OEM-specific escalation contacts for Dell, HP, and Lenovo if your Winre.wim move fails on a vendor-locked image.