Windows 11 security update leaves virtual machines unable to boot

Facepalm: A recent Windows 11 security update has left some users facing unexpected trouble: their computers refuse to boot. The update in question, KB5058405, was automatically rolled out to devices running Windows 11 versions 23H2 and 22H2. Instead of simply improving security, it has triggered a critical error for a subset of users.

The problem arises after installation, when affected PCs halt during startup and display a recovery error with the code 0xc0000098. This message typically indicates that a required file – often ACPI.sys, a crucial system driver responsible for managing hardware resources and power states – is missing or corrupted. Some users have reported seeing the same error code referencing other system files, suggesting the issue may not be limited to ACPI.sys alone.

Microsoft has acknowledged the problem, stating that it primarily impacts devices running in virtual environments. The most vulnerable systems include virtual machines hosted on Azure Virtual Machines, Azure Virtual Desktop, and on-premises solutions using Citrix or Hyper-V.

According to Microsoft, users with Windows 11 Home or Pro editions are unlikely to encounter the issue, as virtual machines are not typically used in consumer setups.

While Microsoft describes the number of affected devices as "small," the exact scale remains unclear. IT professionals and administrators have reported the error in online forums, sharing their experiences and seeking advice.

So far, Microsoft has not released a fix or official workaround. The company says it is actively investigating the cause and working toward a solution. In the meantime, some IT pros have suggested temporary measures, such as rolling back the update or using recovery tools to repair boot files, but these steps carry risks and may not resolve the issue in every case.

This incident follows a pattern seen with previous Windows updates, where urgent security fixes have occasionally led to unforeseen technical problems. The challenge of balancing a rapid response to security threats with the need for reliable updates remains a difficult one for Microsoft and its users.

For now, organizations and users managing virtual environments are advised to closely monitor Microsoft's support channels for updates. Those who have not yet installed the update may wish to defer it temporarily and ensure that essential data is backed up as a precaution. Microsoft encourages users experiencing the issue to report it through official support channels to aid in the investigation.