Windows 10: .NET-Framework Updates KB4598301 and KB4598299 are causing crashes

[German]The .NET Framework updates KB4598301 (Jan. 2021) and KB4598299 (Feb. 2021) are proving to be a problem for some users, causing crashes (STATUS_FATAL_USER_CALLBACK_EXCEPTION) in WPF applications built with Visual Studio.


Updates KB4598301 and KB4598299

Update KB4598301  is a cumulative preview update for .NET Framework 3.5 and 4.8 for Windows 10, version 1909, and Windows Server, version 1909. I had not addressed the update, which was released on January 26, 2021, here on the blog. The update includes the following reliability improvements in .NET Framework 3.5 and 4.8.

  • ASP.NET: Addresses an issue where after installing the update released on October 20th, some ASP.Net applications fail during precompilation – likely with a message that contains the words "Error ASPCONFIG."
  • Windows Presentation Foundation (WPF): Addresses a hang when scrolling to the end of a TreeView, when layout rounding is enabled and DPI scaling is not 100%.
  • Windows Presentation Foundation (WPF): Common Language Runtime (CLR)::Improves the reliability of automatic Native Image generation task.

The update is (according to Microsoft) optionally offered via Windows Update in an update search, but is also available for download in the Microsoft Update Catalog. Only in WSUS would a manual import via 4598301 be required. Microsoft's recommendation is to apply this update as part of regular maintenance routines – my advice would have been to rather avoid installing this update. However, users in unmanaged Windows 10 environments have no choice, provided the update is installed automatically and then triggers a reboot (see Windows 10 and the crux of automatic .NET Framework preview update installations).

Update KB4598299 is a cumulative preview update for .NET Framework 3.5 and 4.8 for Windows 10, version 2004, Windows Server, version 2004, Windows 10, version 20H2, and Windows Server, version 20H2. It was released on February 2, 2021, and is described in the blog post Windows 10 Update KB4598291 and .NET Update KB4598299. It contains virtually the same reliability improvements in .NET Framework 3.5 and 4.8 as I described for update KB4598301. The same applies to distribution and autoinstallation as described above. The update requires a reboot after installation. For both preview updates, Microsoft tells us in the KB articles "Microsoft is not currently aware of any issues in this update".

Updates KB4598301 and KB4598299 crashes VS/WPS apps

I had already noticed it last Friday at Bleeping Computer: Visual Studio or WPF applications crash on Windows 10 and Windows Server when docking or dragging windows after installing the .NET Framework updates mentioned above. That's according to this post from a user in the Visual Studio developer community, among others. 

WPF Window crashes on closing after installing KB4598299

I have developed a software in WPF (Framework 4.6.1, Visual Studio 2019 16.8.4, Windows 10 20H2 19042.789) which opens a WPF window on the main screen which in turn opens another WPF window on the secondary screen.
When the first window closes, the Close method of the window on the second screen is called. Until yesterday I had no error problems but since this morning (I have not changed any line of code), since I installed the KB4598299, the program goes into exception on closing the second window.

Microsoft's Jeff Robinson then confirms in a reply that the user is a victim of the same WPF bug that was distributed in the latest Windows updates and affects Visual Studio. In the post, Robinson gives advice on how to avoid the bug by installing a config file with special content in the same directory as the WPF application.


In this post  of a thread in the developer community, someone reports a STATUS_FATAL_USER_CALLBACK_EXCEPTION (0xc000041d) bug in Visual Studio. In this post, Robinson also confirms the bug and that they have found the root cause. 

We have identified the root cause in KB4598301 and are working to get a fix released. We're also working to release VS updates that will make it invulnerable to the KB's bug.

Also there he gives the hint how the crash of the Visual Studio IDE can be avoided by a modified devenv.exe.config (details can be read in the linked posts). 

Similar articles:
Windows 10 Update KB4598291 and .NET Update KB4598299
Windows 10 and the crux of automatic .NET Framework preview update installations

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