Microsoft warns that the KB5012643 update is causing problems with lots of Windows 11 apps

It is not long since Microsoft released the KB5012643 update for Windows 11, bringing with it a lengthy list of improvements and security fixes. But, as has been the case with so many Windows updates, it also brought problems.

We have already seen issues with screen flicker in Safe Mode, although Microsoft has taken steps to address this. But now the company has issued a warning that Windows 11 users may experience issues with certain types of apps after installing the KB5012643 update.

See also:

• Microsoft issues a fix for Windows 11 Safe Mode problems caused by KB5012643 update
• Microsoft offers advice for ditching Internet Explorer before it is retired next month
• Microsoft releases new PowerToys v0.58.0, fully embracing .NET 6, fixing a huge number of bugs, and pleasing Windows 11 users

Microsoft has not made a big announcement, but it has added a note to the Known Issues section of the Release Health page for Windows 11 version 21H2. The title of the issue informs users that following the installation of KB5012643, "some .NET Framework 3.5 apps might have issues".

Going into a little more detail, Microsoft explains:

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.

While Microsoft says that the problem has been assigned a status of "Mitigated", the mitigating action suggested is to simply uninstall the update:

Workaround: To mitigate this issue, you can uninstall KB5012643. To do this, select the Start button and type, Windows Update Settings, and select it. On the Windows Update settings window, select View Update History then select Uninstall Update. Find KB5012643 in the list and select it, then select Uninstall.

Microsoft goes on to say:

If you cannot uninstall KB5012643, you can also mitigate this issue by re-enabling .NET Framework 3.5 and the Windows Communication Foundation in Windows Features. For instructions, please see Enable the .NET Framework 3.5 in Control Panel. Advanced users or IT admins can do this programmatically using an elevated Command Prompt (run as administrator) and running 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

This is not the end of the story. Microsoft says that it is "working on a resolution and will provide an update in an upcoming release".

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