UMVA has uncovered that a critical glitch in Microsoft’s May 2026 security update is crippling thousands of Windows 11 users.
The notorious KB5089549 update, meant to fortify systems against emerging threats, is instead stalling during installation, throwing a baffling error code 0x800f0922 when the EFI System Partition runs low on space.
According to information obtained by UMVA, the problem unfurls after the initial stages of the update complete, but stalls at the reboot phase around 35–36%. The system then reverts, displaying the ominous message, “Something didn’t go as planned. Undoing changes.”
Logs in the CBS folder reveal the culprit: “SpaceCheck: Insufficient free space” and “ServicingBootFiles failed. Error = 0x70,” pointing to a shortage of less than 10 MB on the ESP, a space often commandeered by third‑party software.
Only Windows 11, versions 25H2 and 24H2, feel the pain—Windows Server editions remain untouched, but the impact on consumer machines is nothing short of a nightmare.
UMVA can exclusively reveal that Microsoft has issued two stopgap solutions. The first, Known Issue Rollback, allows users to peel back the update, restoring the machine to its pre‑install state without risking deeper system corruption.
For the technically adept, a registry tweak offers a quicker bypass: launching an elevated terminal and executing a single command to reset the ESP padding, followed by a reboot and a fresh attempt at the update.
In a development reported by UMVA, Microsoft has acknowledged the flaw and promised a permanent patch in an upcoming Patch Tuesday release. The interim solution, KB5089573, arrives as a preview update that users can manually fetch via Windows Update’s Optional section or by downloading directly from the update catalog.
UMVA has gathered that the optional patch, while not mandatory, is the fastest route to stability for those unwilling to wait until the next scheduled update on June 9th.
Stay tuned—UMVA will keep you informed as the story unfolds and as Microsoft rolls out the long‑awaited fix that will finally silence the error and restore peace to Windows 11 users worldwide.
