.NET Framework October 2019 Cumulative Updates Windows 10 version 1903 and Windows 10 version 1909

Tara Overfield

Today, we are releasing the October 2019 Cumulative Updates for .NET Framework 3.5 and 4.8 on Windows 10 version 1903 and Windows 10 version 1909

Quality and Reliability

This release contains the following quality and reliability improvements.


  • Addresses an issue with ValidationContext.MemberName when using custom DataAnnotation.ValidationAttribute.


  • Reduces the risk of returning unordered ConstructorInfo’s from Type.GetConstructors().
  • Improved behavior in scenarios where external bugs (such as a double-free) prevent underlying OS threads from starting. The runtime now fails with a diagnostic error rather than hanging waiting for the thread to start. This allows better failure recovery and better diagnostics of the problem that caused the failure.
  • Addresses and issue with late bound .NET COM calls containing SafeArrays where the SafeArray is not fully initialized.

Windows Forms

  • Addresses an issue that prevented navigation to the last item of the dropped-down menu item by single up-arrow key press.
  • Addresses and issue where the property grid can throw a NullReferenceException when selection changes to null (nothing is selected) in response to value changes


  • Addresses and issue where software rendering fails to draw images whose position and scaling are too large. For example, an Image element with Width=10, sourced to a bitmap with width=500 and positioned 700 pixels from the left edge of the enclosing window, fails to appear because the scaling factor S = 500/10 = 50 and the position X=700 are too large, in the sense that their product S * X = 50 * 700 = 35000 exceeds 2^15 = 32768.

1 Common Language Runtime (CLR)
2 Windows Presentation Foundation (WPF)

Getting the Update

The Cumulative Update is available via Windows Update, Windows Server Update Services (WSUS) and Microsoft Update Catalog.

Microsoft Update Catalog

You can get the update via the Microsoft Update Catalog. For Windows 10, NET Framework 4.8 updates are available via Windows Update, Windows Server Update Services, Microsoft Update Catalog. Updates for other versions of .NET Framework are part of the Windows 10 Monthly Cumulative Update.

Note: Customers that rely on Windows Update and Windows Server Update Services will automatically receive the .NET Framework version-specific updates. Advanced system administrators can also take use of the below direct Microsoft Update Catalog download links to .NET Framework-specific updates. Before applying these updates, please ensure that you carefully review the .NET Framework version applicability, to ensure that you only install updates on systems where they apply.

Product Version Cumulative Update
Windows 10 1909 and Windows Server, version 1909 4522742
.NET Framework 3.5, 4.8 Catalog 4519573
Windows 10 1903 and Windows Server, version 1903 4522741
.NET Framework 3.5, 4.8 Catalog 4519573

Previous Monthly Rollups

The last few .NET Framework Monthly updates are listed below for your convenience:

1 comment

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  • Thomas De Wulf 0

    I really would like to have an update on UWP with .NET Standard 2.1 compatibility by now….

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