Microsoft Issues Out-of-Band Patches for Windows 11 Startup Failure
In the realm of Windows administration, recent events have sparked a flurry of activity following a faulty update released during May’s Patch Tuesday. Microsoft has swiftly responded to the fallout by issuing out-of-band updates to rectify a critical issue affecting Windows 11 systems running versions 22H2/23H2, particularly in virtual environments.
The crux of the problem lies in the installation of the May Windows security update (KB5058405), which triggers a false alarm within the operating system regarding the absence of a pivotal file – ACPI.sys. This file, essential for the Advanced Configuration and Power Interface, is imperative for Windows to manage hardware resources and power states. Consequently, affected systems fail to boot, displaying error code 0xc0000098 due to the missing file.
Microsoft has acknowledged reports of similar errors involving different file names and highlighted that the issue primarily impacts devices in virtual environments, including Azure Virtual Machines, Azure Virtual Desktop, and on-premises virtual machines hosted on Citrix or Hyper-V.
To address this issue, Microsoft has rolled out specific fixes – KB5027397 for version 23H2 and KB5062170 for version 22H2 – exclusively available through the Microsoft Update Catalog. For users who haven’t yet installed the May 2025 security updates and operate within a virtual desktop infrastructure, applying the out-of-band updates is paramount.
The out-of-band update not only resolves the startup failure issue but also incorporates all enhancements and fixes from the May 2025 Windows non-security preview update. As a cumulative update, administrators can directly install KB5062170 without the need for any prior updates, as it supersedes all previous patches for the affected versions, necessitating a device restart post-installation.
Microsoft has assured that users of Windows Home or Pro editions are less likely to encounter this issue, as they are less prone to running virtual machines, thus minimizing the impact on a wider user base.
The occurrence of such incidents prompts reflection on the testing processes of major software vendors, including Microsoft. While rigorous testing precedes updates, human error and unforeseen edge cases can still slip through the cracks. Tyler Reguly, associate director of security R&D at Fortra, emphasizes the inevitability of human fallibility in testing at scale and advocates for transparent Root Cause Analysis to prevent recurrence.
Gene Moody, field CTO at Action1, underscores the complexity inherent in real-world systems that often eludes simulated test environments. He emphasizes the significance of progressive rollout strategies, robust telemetry, and swift rollback capabilities to navigate the unpredictability of diverse system configurations and environmental factors.
In conclusion, the recent out-of-band patches issued by Microsoft serve as a stark reminder of the intricate interplay between software updates and real-world system dynamics. As IT professionals navigate the evolving landscape of technology, adaptability, resilience, and a proactive approach to addressing unforeseen challenges remain paramount in ensuring seamless operations and business continuity.