Microsoft released an optional preview update on May 26, 2026, that directly addresses a frustrating installation failure plaguing Windows 11 versions 24H2 and 25H2. The fix, delivered as KB5089573, resolves a defect that caused the critical May 12 security update KB5089549 to roll back on affected PCs, leaving systems potentially unpatched and throwing the error code 0x800f0922.

The May 2026 Patch Tuesday Rollback Fiasco

IT administrators and end users began reporting widespread issues shortly after KB5089549 was pushed via Windows Update on May 12, 2026. The cumulative security update, intended to plug multiple vulnerabilities, repeatedly failed to install on a subset of devices. In typical fashion, Windows would download the update, reboot to apply it, but then revert changes with the message "We couldn't complete the updates. Undoing changes." The error 0x800f0922 appeared in Windows Update history and event logs, signaling a generic installation failure tied to disk space or servicing stack problems—but in this case, it was a bug within the update itself.

For many, the rollback meant that critical security patches for Windows Defender, Kernel, and other components were not applied. With cyber threats evolving rapidly, any delay in deploying security updates opens a window of risk. Home users experienced endless update loops, while enterprise IT teams scrambled to shield unpatched machines. Microsoft's official Windows Health Dashboard eventually acknowledged the issue, noting that KB5089549 might fail to install on devices with SYSTEM or reserved partitions that did not meet certain attributes—though the precise root cause remained under investigation.

KB5089573 Arrives as the Lifeboat

The May 26, 2026, monthly preview update (often referred to as “C” or “D” week release) KB5089573 includes the long-awaited correction. Microsoft designed this optional update specifically to prevent the 0x800f0922 error during installation of KB5089549 and subsequent cumulative updates. While preview updates are non-security and not pushed automatically, they serve as a test bed for fixes slated for the next Patch Tuesday. Installing KB5089573 ensures that the servicing stack and component handling are patched so that the rollback no longer occurs.

This update is targeted at Windows 11 version 24H2 (the major 2024 feature update) and version 25H2 (the 2025 feature update), both of which share a common servicing foundation. Microsoft’s release notes for KB5089573 explicitly call out the resolution: “Addresses a known issue that might cause Windows update installation to fail with error 0x800f0922 on certain devices when installing KB5089549.”

The Technical Underpinnings of Error 0x800f0922

Error 0x800f0922 has historically been linked to insufficient free space on the system drive or an undersized System Reserved partition. During cumulative updates, the component store (C:\Windows\WinSxS) grows temporarily, and if Windows cannot allocate enough scratch space, the update aborts. However, in this incident, the problem traced back to a logic flaw in how KB5089549 assessed available capacity and managed the component store on devices with System Reserved partitions sized under 500 MB—a common configuration from older Windows 10 upgrades or OEM images. The update incorrectly calculated required space post-download, triggering an abort even when dozens of gigabytes were free.

Microsoft’s servicing team reworked the space estimation algorithm and modified the deployment sequence so that the update no longer demands unrealistic free space. The fix in KB5089573 also improves cleanup routines, ensuring that temporary files from the failed attempt do not consume additional space. For IT pros, this highlights the importance of monitoring partition sizes, but the patch eliminates the need for manual repartitioning in most cases.

How to Obtain and Install KB5089573

KB5089573 is available through three primary channels:

  • Windows Update for Consumers: Go to Settings > Windows Update, select “Check for updates,” and if the optional update is offered, click “Download and install.” Because it is an optional preview, you must manually opt in unless you’ve enabled the “Get the latest updates as soon as they’re available” toggle.
  • Microsoft Update Catalog: The standalone MSU package can be downloaded from catalog.update.microsoft.com by searching for “KB5089573” and selecting the correct architecture (x64, ARM64) for your device. This method is favored by administrators who need to deploy via SCCM, WSUS, or offline media.
  • Windows Update for Business: Organizations can import the update into their management tools, testing it before broader rollout. The fix will eventually be bundled into the June 2026 Patch Tuesday release, making this preview a crucial validation step.

After installation, a restart is required. Users who previously experienced the rollback should then be able to install KB5089549 without error—or they can rely on KB5089573 since it already includes the security fixes from its predecessor (preview updates are cumulative and contain all prior patches).

Workarounds That Fell Short

Before KB5089573 became available, affected users and IT forums buzzed with unofficial remedies. Some succeeded by expanding the System Reserved partition using third-party partition tools or by assigning a drive letter to the SYSTEM partition and manually running DISM cleanup commands. Others cleared the SoftwareDistribution folder or ran the Windows Update Troubleshooter. These methods worked for only a fraction of devices and often required administrative courage that many end users lack. Microsoft’s own guidance in the Health Dashboard recommended ensuring at least 20 GB of free space on the C: drive and temporarily disconnecting external storage, but for most impacted machines, the real culprit was the partition size check bug.

KB5089573 renders these workarounds obsolete. The root cause is addressed in the servicing stack, so no partition resizing or manual script execution is needed. Still, the episode underscores how fragile update mechanisms can be when edge-case hardware configurations aren’t fully tested.

Impact on Enterprise and Managed Environments

For organizations standardized on Windows 11 24H2 or migrating to 25H2, the May 2026 update rollback created a compliance nightmare. Security auditors flagged unpatched CVEs, and support desks fielded calls about devices stuck in “undoing changes” loops. Some administrators paused all Windows updates via policy until the issue was resolved, ironically leaving systems even more exposed.

With KB5089573, IT teams can resume normal patching cadences. The update’s optional status allows them to test on a pilot group, verify that the rollback disappears, and then plan deployment before the mandatory June Patch Tuesday. Additionally, the fix helps maintain configuration baselines because it eliminates the need to manually modify disk partitions—a change that can cause pain with disk encryption or recovery environments.

Monitoring via the Windows Health Dashboard

Microsoft maintains a public dashboard at admin.microsoft.com under “Windows release health” (accessible to licensed Microsoft 365 customers). In the days following KB5089549’s release, the dashboard updated with entry ID WI125894, detailing the 0x800f0922 installation failure. The entry confirmed that devices with system partitions smaller than 500 MB were affected and that an upcoming preview update would contain the fix. As of May 26, the dashboard reflects that the issue is resolved with KB5089573, and the status has been changed to “mitigated” for users who install the optional update.

For those who cannot immediately deploy the preview, the dashboard recommends waiting for the June 10, 2026, security update, which will roll up the fix. However, Microsoft warns that the security update will be mandatory, so the installation failure could recur if the fix is not preinstalled. Therefore, early adoption of KB5089573 is strongly advised.

A Broader Look at Windows 11 Servicing in 2026

Windows 11 version 24H2 (released in fall 2024) introduced sweeping changes to the servicing model, including checkpoint cumulative updates and revamped feature update deployment. Version 25H2, which arrived in late 2025, built on that foundation with improved Windows Defender Application Control and a more resilient servicing stack. Yet, as this rollback incident shows, even modern servicing architectures are not immune to bugs when a niche condition slips through testing.

Microsoft’s aggressive pace of monthly updates—security on Patch Tuesday, optional previews in the third and fourth weeks—means that corner cases can emerge after millions of devices receive the update. The quick turnaround from the May 12 issue report to the May 26 fix demonstrates a responsive servicing team, but the week of exposure underscores the risk of delayed patching. For users, it reinforces the value of keeping device configurations standardized and heeding Microsoft’s recommended partition sizes during OS deployments.

Conclusion

KB5089573 is more than just another optional update; it is the key to breaking the installation deadlock that left many Windows 11 machines vulnerable in May 2026. By correcting the erroneous space calculation and component store handling, the patch ensures that KB5089549 and future cumulative updates can install smoothly on all 24H2/25H2 devices, regardless of partition sizes within supported limits.

Users who have been stuck in the rollback loop should prioritize installing this preview update. IT administrators should test and deploy it to restore their security posture ahead of the June Patch Tuesday mandatory rollout. As always, backup critical data before applying any system update, and monitor the Windows Health Dashboard for any late-breaking complications. For detailed installation instructions or direct downloads, search for KB5089573 on the Microsoft Update Catalog.