.NET Framework October 2019 Security and Quality Rollup

Brett Lopez

Today, we are releasing the October 2019 Security and Quality Rollup and Cumulative Updates for .NET Framework.


No new security fixes. See September 2019 Security and Quality Rollup for the latest security updates.

Quality and Reliability

This release contains the following quality and reliability improvements.


  • Addresses an issue that affects thread contention that occurs in BinaryFormatter.GetTypeInformation by using ConcurrentDictionary to handle multi-thread access.


  • Addresses an issue that might cause handle leaks to occur in scenarios that repeatedly load and unload Mscoree.dll.
  • Addresses rare cases that incorrectly cause process termination instead of delivering the expected NullReferenceException result.


  • Addresses an issue that affects a WPF ComboBox (or any Selector) within a DataGrid cell that can try to change its selection properties (SelectedIndex, SelectedItem, SelectedValue) when the cell’s data item is re-virtualized or removed from the underlying collection. This can occur if the Selector’s ItemSource property is data bound through the cell’s DataContext setting. Depending on the virtualization mode and the bindings that are declared for the selection properties, the symptoms can include unexpected changes (to null) of the data item’s properties, and unexpected displays (as null) of other data items that re-use the UI that was previously attached to the re-virtualized item.
  • Addresses an issue in which a WPF TextBox or RichTextBox element that has spell checking enabled crashes and returns an “ExecutionEngineException” error in some situations, including inserting text near a hyperlink.
  • Addresses an issue that affects Per-Monitor Aware WPF applications that host System-Aware or Unaware child windows and that run on .NET Framework 4.8. This .NET version occasionally crashes and returns a “System.Collections.Generic.KeyNotFoundException” exception.

1 Base Class Library (BCL)
2 Common Language Runtime (CLR)
3 Windows Presentation Foundation (WPF)

Getting the Update

The Security and Quality Rollup is available via Windows Update, Windows Server Update Services, 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. The following table is for Windows 10 and Windows Server 2016+ versions.

Product Version Cumulative Update
Windows 10 1903 and Windows Server, version 1903 Catalog 4524100
.NET Framework 3.5, 4.8 Catalog 4515871
Windows 10 1809 (October 2018 Update) Windows Server 2019 Catalog 4524099
.NET Framework 3.5, 4.7.2 Catalog 4515855
.NET Framework 3.5, 4.8 Catalog 4515843
Windows 10 1803 (April 2018 Update)
.NET Framework 3.5, 4.7.2 Catalog 4520008
.NET Framework 4.8 Catalog 4524098
Windows 10 1709 (Fall Creators Update)
.NET Framework 3.5, 4.7.1, 4.7.2 Catalog 4520004
.NET Framework 4.8 Catalog 4524097
Windows 10 1703 (Creators Update)
.NET Framework 3.5, 4.7, 4.7.1, 4.7.2 Catalog 4520010
.NET Framework 4.8 Catalog 4524096
Windows 10 1607 (Anniversary Update) Windows Server 2016
.NET Framework 3.5, 4.6.2, 4.7, 4.7.1, 4.7.2 Catalog 4519998
.NET Framework 4.8 Catalog 4524095

The following table is for earlier Windows and Windows Server versions.

Product Version Security and Quality Rollup
Windows 8.1, Windows RT 8.1 and Windows Server 2012 R2 Catalog 4524104
.NET Framework 3.5 Catalog 4507005
.NET Framework 4.5.2 Catalog 4506999
.NET Framework 4.6, 4.6.1, 4.6.2, 4.7, 4.7.1, 4.7.2 Catalog 4515853
.NET Framework 4.8 Catalog 4515846
Windows Server 2012 Catalog 4524103
.NET Framework 3.5 Catalog 4507002
.NET Framework 4.5.2 Catalog 4507000
.NET Framework 4.6, 4.6.1, 4.6.2, 4.7, 4.7.1, 4.7.2 Catalog 4515852
.NET Framework 4.8 Catalog 4515845
Windows 7 SP1 Windows Server 2008 R2 SP1 Catalog 4524102
.NET Framework 3.5.1 Catalog 4507004
.NET Framework 4.5.2 Catalog 4507001
.NET Framework 4.6, 4.6.1, 4.6.2, 4.7, 4.7.1, 4.7.2 Catalog 4515854
.NET Framework 4.8 Catalog 4515847
Windows Server 2008 Catalog 4524105
.NET Framework 2.0, 3.0 Catalog 4507003
.NET Framework 4.5.2 Catalog 4507001
.NET Framework 4.6 Catalog 4515854

Previous Monthly Rollups

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


Discussion is closed. Login to edit/delete existing comments.

  • Денис Перевозчиков 0

    “Addresses an issue that affects Per-Monitor Aware WPF applications that host System-Aware or Unaware child windows and that run on .NET Framework 4.8. This .NET version occasionally crashes and returns a “System.Collections.Generic.KeyNotFoundException” exception.”
    Will this fix be applied to .NET Core WPF also? I rarely see this exception occurs too

  • Arash Laylazi 0

    Every month, I have searching “Cumulative Update for .NET Framework for Windows 10 Version 1903 x64” on MS Update Catalog website to download latest updates.
    In this article, you have introduced “KB4524100”, and the latest item on MS Update Catalog website is “KB4524100”, But it leads to download the file related to “KB4515871”.
    Are these two equivalent?

    • Brett LopezMicrosoft employee 0

      Hi Arash, thanks for your question. The short answer is, yes – the contents that released broadly this week’s are equivalent, and in fact the very same this time, as what was released on Sept 26th as a limited distribution release. The new KB number (KB4524100) helps distinguish this week’s broad roll-out. In many cases there are new security fixes shipping as part of second Tuesday broad releases, but not this time around. More info about the general update cadence here: https://techcommunity.microsoft.com/t5/Windows-IT-Pro-Blog/Windows-10-update-servicing-cadence/ba-p/222376. Hope that helps, let us know if you have any other questions.

      • Arash Laylazi 0

        Thanks a lot.

  • Ryan Crowther Jr 0

    Just a quick heads up to avoid any possible confusion! It would appear at the time of this post, that the KB Article links for all “earlier Windows and Windows Server versions,” point to the relevant September 2019 Preview of Quality Rollup articles, not the relevant October 2019 Security and Quality Rollup articles.

    • Brett LopezMicrosoft employee 0

      Hi Ryan, thank you very much for pointing this out! The top level KB links are now updated on the “earlier versions” table (i.e. 4524102,4524103,4524104,4524105). Note that .NET version-specific KBs remain the same. As noted in the comment to Arash, the October 8th release is the broader rollout for the same content that released to a limited audience as the Sept 2019 preview release (there is no new security content this time around in October). Please let us know if we can add any further clarifications. Thanks!

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  • Varadharaja Perumal 0

    Hi all,
    I had this problem earlier too but was able to resolve it after reading this blog – that is the issue of Forms designer not appearing.
    But, here again I the problem has rec-cured weirdly
    I am doing my application – created a simple forms with minimal forms design objects and concentrated on developing the code in c# and have been developing and testing the same for last couple of week lets say. No problem, but strangely now the same application refuses to open the forms design to let me modify the forms, though the forms opens up when i run the code – but that’s no use if i cannot redesign the form further to complete the application.
    I have also tried to create a new application – same happens – initially the forms appears, i create the minimal forms objects, and then i try to copy the original code into the new one and the forms designer just does not appear – strange really.
    Can some one please help and suggest how to get over the problem. I am stuck as it is a large amount of code and i have to test it out with all other form objects created too.
    thank you all for any help in this regard

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