Microsoft has warned users running Windows 11, version 21H2, who have installed the KB5012643 update, that they may have problems launching and using some applications.

“After installing KB5012643, some NET Framework 3.5 apps might have issues or might fail to open,” Microsoft explained on the Windows Health Dashboard.

Applications affected by the update include apps that use optional components such as Windows Workflow (WWF) and Windows Communication Foundation (WCF).

The KB5012643 update also makes some Windows applications, such as File Explorer, Start Menu, and Taskbar, look unstable while running in safe mode.

To mitigate the issue, Microsoft is asking users to uninstall the problematic KB5012643 update. This will help restore functionality to the NET Framework 3.5 apps.

Those who cannot uninstall this cumulative update immediately can mitigate the problem by reactivating NET Framework 3.5 and the Windows Communications Foundation from the Windows Features dialog.