Windows 11: Preview Update KB5012643 causes issues with .NET Framework 3.5 applications

Windows[German]The preview update KB5012643 for Windows 11, released on April 25, 2022, turns out to be a real problem bear. First there were display problems in Safe Mode, which had to be corrected by KIR. Now it turns out that the preview update also causes problems with .NET Framework 3.5 applications. Microsoft has also confirmed this in the meantime and tried to give hints on how the update can still be uninstalled.


Preview update KB5012643 for Windows 11

Preview update KB5012643 for Windows 11  raises the OS build to 22000.652 and provides a number of bug fixes for these versions of Windows. I had reported on this update and the fixes it provides in the blog post Windows 11 Preview Update KB5012643 (April 25, 2022). So there are fixes for Secure Boot, fixes for bugs with video playback or display problems with windows and also the 40 minutes boot time for POS terminals has been fixed. The list of fixes should certainly convince users and administrators to install this optional preview update.

Unfortunately, it appears that this is not a very good idea. In the article Windows 11: Preview update KB5012643 causes display issues in safe mode, I had already reported that the safe mode in Windows 11 becomes unusable due to this update – the display flickers. Microsoft has confirmed the issue and rolled it back via the Known Issue Rollback (KIR) feature.

Issues with .NET Framework 3.5 applications

In a new post Some .NET Framework 3.5 apps might have issues in the Know Issues section of the Windows 11  status area, Microsoft now confirms another issue and writes.

After installing KB5012643, some .NET Framework 3.5 apps might have issues or might fail to open. Affected apps are using certain optional components in .NET Framework 3.5, such as Windows Communication Foundation (WCF) and Windows Workflow (WWF) components.

What can you do, if you are affected?

Uninstall update KB5012643

Microsoft suggests in the article to mitigate this problem by uninstalling update KB5012643. To do this, follow the steps below:


  1. After clicking the Start button, enter Windows Update Settings and select the search result.
  2. In the Windows Update settings window, select the option Show update history and then the option Uninstall update.
  3. Then search for the entry for KB5012643 in the list, select it and click the Uninstall button.

After uninstalling, you can test whether the problem has been fixed. If not, restart Windows 11 if necessary.

Update cannot be uninstalled

For the cases where the above uninstall steps are not available, Microsoft suggests repairing by re-enabling .NET Framework 3.5 and Windows Communication Foundation in Windows Features (accessible from Control Panel). Advanced users or IT administrators can open a command prompt via Run as administrator and enter the following commands:

dism /online /enable-feature /featurename:netfx3 /all
dism /online /enable-feature /featurename:WCF-HTTP-Activation
dism /online /enable-feature /featurename:WCF-NonHTTP-Activation

In this case, a restart of the Windows 11 (21H1) client is required. (via)

Similar articles
Windows 11 Preview Update KB5012643 (April 25, 2022)
Windows 11: Preview update KB5012643 causes display issues in safe mode

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