Microsoft has officially confirmed a critical issue affecting enterprise and managed environments running Windows 11 versions 24H2 and 25H2.
The bug, first triggered by cumulative updates released in July 2025, causes widespread failures in essential UI components, rendering the desktop unusable for many users.
According to an updated support document released on December 2, 2025, the issue stems from a timing failure in the registration of XAML-dependent packages.
When these updates are applied, the necessary Extensible Application Markup Language (XAML) dependencies, specifically packages like MicrosoftWindows.Client.CBS fails to register before the Windows Shell initializes. This race condition effectively breaks the visual layer of the operating system before the user can even interact with it.
Windows 11 25H2 UI Features Broken
The core of the problem lies in the dependency chain between the Windows Shell and its underlying AppX packages. Modern Windows interface elements, such as the Start Menu and Taskbar, rely on “CBS” (Component Based Servicing) client packages to render their UI.
Microsoft identified that the following specific dependencies are failing to register in time during the logon sequence:
- MicrosoftWindows.Client.CBS_cw5n1h2txyewy
- Microsoft.UI.Xaml.CBS_8wekyb3d8bbwe
- MicrosoftWindows.Client.Core_cw5n1h2txyewy
When Explorer.exe or SiHost.exe (the Shell Infrastructure Host) attempts to call these missing resources, the processes crash or hang, leading to a “black screen” state or a non-functional desktop.
While personal devices are largely unaffected, the impact on enterprise environments is significant. The issue is most prevalent in Virtual Desktop Infrastructure (VDI) and other non-persistent OS installations.
In these environments, where a fresh OS instance is provisioned for every user logon, the race condition occurs repeatedly because the application packages must be reinstalled and registered at every single sign-in event.
Below is the breakdown of failure signatures administrators may encounter:
| Binary Component | Failure Signature / User Experience |
|---|---|
| Explorer.exe | Users log on to a completely black screen; Taskbar fails to render; Explorer crashes immediately upon start. |
| StartMenuExperienceHost | The Start menu fails to open or displays a “Critical Error” message to the end-user. |
| ShellHost.exe | The Shell Infrastructure Host crashes repeatedly, preventing UI initialization. |
| Consent.exe | The User Account Control (UAC) dimming screen and prompt fail to appear. |
| SystemSettings | The Settings app (Start > Settings) fails to launch silently with no error message. |
| XAML Apps | various modern inbox apps crash immediately upon initialization. |
Microsoft is currently developing a permanent resolution, but has not provided a specific timeline for the fix. In the interim, IT administrators must manually intervene to restore functionality.
For persistent environments, administrators can manually register the missing packages via PowerShell by targeting the AppxManifest.xml files in the C:\Windows\SystemApps\ directory.
For non-persistent VDI environments, where manual intervention per session is impossible, Microsoft recommends a synchronous logon script.
This script acts as a wrapper, forcibly registering the Microsoft.UI.Xaml and Client.CBS packages before allowing explorer.exe to launch. This sequence ensures the dependencies are fully provisioned, preventing the race condition that leads to the UI failure.
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