KB5089573 Fixes Windows 11’s Patch Tuesday Reboot Fail

KB5089573 release notes for Windows 11 confirm Microsoft, Windows 11’s maker, shipped its May 26, 2026 preview cumulative update for Windows 11 24H2 and 25H2 to fix a Patch Tuesday install failure that can roll systems back with error 0x800f0922 when the EFI System Partition has too little free space.

For home users, the fix should mean fewer failed restarts. For IT teams, the update is a reminder that boot partitions, firmware trust, update channels, and Copilot-era system components now meet in the same maintenance window.

A Patch Fix That Starts in the EFI Partition

The failure Microsoft is cleaning up began with the May 12 security release, not with the optional preview itself. In the May Patch Tuesday known issue notes, Microsoft says some devices installed the first phases, failed during restart at about 35 to 36 percent, rolled back, and ended on the 0x800f0922 code.

The useful clue sits in a place most Windows users never open. EFI means Extensible Firmware Interface, and the EFI System Partition (ESP, the small boot partition that holds startup files) can block servicing when it is crowded by vendor files or old boot material. Microsoft tied the failure to devices with 10 MB or less of available space there.

This places the incident closer to boot servicing than to a normal app crash or driver annoyance. The package had to touch boot-related files during the restart phase. Once Windows decided the partition could not safely take the work, it unwound the install and left admins with logs such as SpaceCheck and ServicingBootFiles failed.

The May Preview Package Compared With Patch Tuesday

The May 26 preview update sits one step after the mandatory security release. The security package moved supported 24H2 and 25H2 machines to one pair of builds; the preview moved them again and removed the install failure from the known issue list.

The table shows why many managed fleets will treat the newer package as a test candidate rather than an emergency push. Microsoft lists it as a non-security preview. It is available through optional updates and the Microsoft Update Catalog, while Windows Update for Business users are told the changes will arrive in the next security update.

AI Components Get a Quiet Version Bump

The install fix is the headline for anyone staring at a rollback screen, but the same package also updates the AI plumbing Microsoft now ships with Windows. Image Search, Content Extraction, Semantic Analysis, and the Settings Model move to version 1.2605.856.0, replacing the 1.2604.515.0 component set listed with the May security release.

The user-facing changes are broader than the AI list. Microsoft says the package accelerates app launch and core shell areas such as Start, Search, and Action Center. WinAddons has already covered how the same release added a Windows 11 Low Latency Profile, a power-management change aimed at making short interactions feel faster.

There is a catch for older hardware. Microsoft notes that AI component updates apply to Copilot+ PCs, its branding for systems with a Neural Processing Unit (NPU, a chip block built for local AI tasks), and do not install on standard Windows PCs or Windows Server.

Secure Boot Turns This Into an Admin Deadline

The boot partition fix lands as Microsoft is also rotating Secure Boot trust. In its Windows Secure Boot certificate guidance, Microsoft says older certificates begin expiring in June 2026, while devices that do not receive newer certificates can keep starting and installing standard Windows updates but may miss future protection for early boot components.

Secure Boot runs in Unified Extensible Firmware Interface (UEFI, the firmware interface that starts before Windows). It checks signatures for pre-OS code such as firmware drivers, boot loaders, and applications before handing control to the operating system. That is why a servicing issue in the boot partition deserves more attention than a cosmetic Windows bug.

The certificate table gives admins dates to pin on the calendar: Microsoft Corporation KEK CA 2011 expires June 24, 2026, Microsoft UEFI CA 2011 expires June 27, 2026, and Microsoft Windows Production PCA 2011 expires October 19, 2026. The May preview adds more high confidence device targeting data so eligible devices can receive newer certificates only after Microsoft sees enough successful update signals.

Deployment Choices for Home PCs and Managed Fleets

Microsoft gives three practical routes for this release: Windows Update, Microsoft Update Catalog, and Windows Server Update Services (WSUS, the Microsoft tool many organizations use to distribute Windows updates). Home users get the shortest path through Settings, then Windows Update, then Advanced options, then Optional updates.

Manual installers have more detail. The Microsoft Update Catalog package list separates downloads by x64 and Arm64 architecture, and Microsoft tells admins who stage Microsoft Update Standalone (MSU, standalone Windows update installer) files to keep the packages in the right order. That is especially relevant for offline media and repair images.

The servicing stack update (SSU, the component package that improves how Windows installs updates) also deserves attention. Microsoft explains in its servicing stack update reference that cumulative updates have included the latest servicing stack payload since February 2021, so most modern devices receive the installer fixes through one combined package.

• Pilot the optional package on a small device ring before approving it fleet-wide.
• Check rollback logs for partition-space messages before blaming drivers or network software.
• Keep Secure Boot and firmware remediation in the same change window as monthly Windows servicing.

Why This Small Fix Matters After the Reboot

The boring path is the one Microsoft wants: an optional update installs, the known issue disappears, and the next security package carries the repaired code to business-managed devices. The Release Health site remains the place to check whether that story changes; Microsoft describes the Windows release health dashboard as its official hub for known issues, safeguards, and servicing milestones.

Still, the incident exposes a Windows maintenance problem that is easy to miss. A few megabytes in a hidden boot partition can decide whether a monthly security update survives restart. That is why admins should treat boot storage, firmware updates, and certificate status as part of patch hygiene, rather than side tasks handled only after a failure.

For everyday users, the most visible gains may come from smaller pieces in the same release. The package also changes Windows Search behavior, and our earlier look at the two-character Windows Search fix shows how Microsoft is using preview updates to ship quality-of-life repairs between security Patch Tuesdays.

If the fix holds through the next mandatory security cycle, the May rollback problem becomes a footnote. If it resurfaces on machines with cramped boot partitions, the next support case will start in the same place: the quiet space Windows reserves before the desktop ever appears.