Microsoft releases emergency fix for Windows 11 startup problems

Following the release of the KB5058405 update last month, Microsoft acknowledged that it was causing problems for some users. Affected users were left with startup issues and a warning of a 0xc0000098 error in the ACPI.sys file.

Now the company has released an out-of-band fix for the issue in the form of the KB5062170 update. Such is the impact of the original problem that Microsoft recommends installing this update in place of the May 2025 security update for Windows 11.

See also:

• No prizes for guessing what's to blame for the latest problem that stops Windows 11 booting (yep, it's another OS update)
• Microsoft says it is ending USB-C confusion with updated Windows 11 WHCP
• Microsoft Security gets a style upgrade that goes beyond the surface to embrace the human

Microsoft has downplayed the issue since acknowledging it, insisting that while some physical devices have been affected, it is primarily something that impacts virtual environments. But with virtualized devices now playing such an important role in so many operations, the effect is still large, with Azure Virtual Machines, Azure Virtual Desktop, and on-premises virtual machines hosted on Citrix or Hyper-V among those environments affected.

Announcing the availability of the fix, Microsoft says:

This issue is resolved in the out-of-band (OOB) update KB5062170, which is only available via the Microsoft Update Catalog.  If you experienced this issue, or if you have not yet deployed the May 2025 Windows security update on the Windows versions listed below and your IT environment includes devices running in a virtual desktop infrastructure, we recommend you apply the out-of-band update instead.

The company adds:

This out-of-band update contains all of the improvements and fixes included in the May 2025 Windows non-security preview update (KB5058502), in addition to this issue’s resolution. Since this is a cumulative update, you do not need to apply any previous update before installing KB5062170, as it supersedes all previous updates for affected versions.

The KB5062170 update is available exclusively from the Microsoft Update Catalog.

If you have installed the problematic KB5058405 update and find yourself with the startup issue, Microsoft has advice here.

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