.NET Framework July 2020 Cumulative Update Preview for Windows 10, version 2004

Tara Overfield

Today, we are releasing the July 2020 Cumulative Update Preview for .NET Framework 3.5 and 4.8 on Windows 10, version 2004.

Quality and Reliability

This release contains the following quality and reliability improvements.


– Use FIPS-compliant hashes in ASP.Net telemetry data.

– Addresses an issue where “Unspecified” was not an allowed value in config for the ‘cookieSameSite’ attribute of the forms authentication and session state configuration sections.


– A change in .NET Framework 4.8 regressed certain EnterpriseServices scenarios where an single-thread apartment object may be treated as an multi-thread apartment and lead to a blocking failure. This change now correctly identifies single-thread apartment objects as such and avoids this failure.

– Addresses an issue in assemblies with IBC profile data causing Ngen worker processes to crash and fall back to full native images.

– Addresses rare crashes that could occur during thread abort delivery.


– SqlBulkCopy.WriteToServer can cause transactions to in-memory SQL tables, to fail. The client may see an exception with message “Execution Timeout Expired. The timeout period elapsed prior to completion of the operation or the server is not responding.” SqlBulkCopy.WriteToServer was sending an Attention token (cancellation message) after sending data to Sql Server, causing the server to abort the transaction for in-memory tables.

Net Libraries

– Addresses a memory leak in HttpListener.


– When using a UPN Windows username with the format similar to username@dns.domain in the username property of a NetworkCredential when using NetTcpBinding or NetNamedPipeBinding, WCF would incorrectly split the username and dns.domain placing them into the UserName and Domain properties. This is invalid in some scenarios and would result in failing to authenticate. This fix removes the credential modification when using a UPN username. The modification can be re-enabled by setting the AppSetting “wcf:enableLegacyUpnUsernameFix” to true.


– Addresses an issue when spell-checking is enabled in WPF TextBox or RichTextBox, words like “etc.”, “e.g.” are identified as spelling errors incorrectly.

– Addresses an issue when some Per-Monitor Aware WPF applications that run on .NET 4.8 may occasionally encounter a crash with exceptionSystem.ComponentModel.Win32Exception.

– Addresses an issue where TextBlock reflows (makes different line-breaking decisions) during render and hit-test, vs. during measure. The symptoms include missing text, and FailFast crashes during programmatic text processing.

– Addresses an issue with a render thread failure caused by HostVisual disconnecting its target on the wrong thread.

– Addresses an issue with a hang while scrolling a TreeView whose tree is non-uniform, in the sense thata given node’s children govern subtrees whose sizes are quite different.

– Addresses an issue with a crash that can occur when closing a tooltip that is re-entrantly closed by user code.

– When an HwndHost leaves the visual tree, a stack trace is created. This is expensive, and usually unnecessary. The logic is now changed to create the stack trace only when the anomalous condition occurs.

– Addresses a memory leak in System.Speech.SpeechSynthesizer.

– DataGrid’s Copy command throws an exception if the system clipboard is locked by another process. This crashes, as there is usually no app code on the stack to catch the exception. The behavior of TextBox (and other apps like Notepad, Word, browsers) in this situation is to fail silently – nothing is copied to the clipboard, but no exception. A WPF app can now opt-in to this behavior by setting in its app.config file.

– Addresses an issue in constructing the internal model for a FixedPage document. Some text was appearing in the wrong order for the purposes of editing operations such as selection and copy/paste.


– Addresses an issue with DataGridView IsReadOnlyaccessibility state: Narrator and other accessible tool announces read-only cell status accordingly.

– Addresses a regression in .NET Framework 4.8 when applications using the DataGridView ComboBox cell type and have opted into Level 3 Accessibility, may experience intermittent crashes while editing the cell.

– Addresses an issue in ClickOnce RFC3161 timestamp verification code.

Windowsforms Accessibility Improvements

In this release we are adding new accessibility improvements that your application can opt-in into. By default these changes are disabled. Applications that opt-in into accessibility features introduced in .NET 4.8 and earlier, can add the following compatibility switch to the application’s config file:


Specifically, if an application targets .NET 4.8, add the following AppContextSwitchOverrides section:

<?xml version="1.0" encoding+"utf-8" ?>
   <supportedRuntime version="v4.0" sku=".NETFramework,Versionv4.8" />
   <!-- AppContextSwitchOverrides value attribute is in the form of key1=true|false;key2=true|false -->
   <AppContextSwitchOverrides value="Switch.UseLegacyAccessibilityFeatures.4=false"/>

If an application targets an earlier version of the framework and opts in into the previously release sets of accessibility features, then add a single “Switch.UseLegacyAccessibilityFeatures.4=false” switch to the existing AppContextSwitchOverrides section:

<?xml version="1.0" encoding+"utf-8" ?>
   <supportedRuntime version="v4.0" sku=".NETFramework,Versionv4.7"/>
<!-- AppContextSwitchOverrides value attribute is in the form of key1=true|false;key2=true|false -->
  <AppContextSwitchOverrides value="Switch.UseLegacyAccessibilityFeatures=false;Switch.UseLegacyAccessibilityFeatures.2=false;Switch.UseLegacyAccessibilityFeatures.3=false;Switch.UseLegacyAccessibilityFeatures.4=false"/>

Winforms accessibility improvements included in this release are: – Addresses an issue with announcing PropertyGrid control items and categories expanded/collapsed state by Screen Readers.

– Updated the accessible patterns of Property Grid control and its inner elements.

– Updated the accessible names of Property Grid control inner elements to correctly announce these by screen reader.

– Addresses bounding rectangle accessible properties for the PropertyGridView controls

– Enables screen readers to announce DataGridView ComboBox cell expanded/collapsed state correctly.

1 Common Language Runtime (CLR) 2 Windows Communication Foundation (WCF) 3 Windows Presentation Foundation (WPF)

Getting the Update

The Cumulative Update Preview is available via Windows Update 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 and Microsoft Update Catalog.

**Note**: Customers that rely on Windows Update 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 2004 and Windows Server, version 2004
.NET Framework 3.5, 4.8 Catalog 4562899


Previous Monthly Rollups

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

July 2020 Cumulative Update Preview

July 2020 Security and Quality Rollup Updates

May 2020 Security and Quality Rollup Updates

March 2020 Update for Windows 10 1607 (Anniversary Update) and Windows Server 2016


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

  • かずお 山内 0

    It’s 10:00 JST, August 1 (1:00 UTC) now, when I click “Check for updates”, this CU preview is not detected on Windows 10 ver 2004.
    It detects a CU for a moment, but it disappears, or 0x8024009 error .I checked again after reboot, download and installation began. Something seems to be wrong. The Windows update history classifies them as other updates, not quality updates. Is the behavior different from that of Windows 10 ver 1909 or earlier?

  • Vreem de Ling 0

    This update is in my list now. But I am NOT going to download a preview for an update? Why a preview? I am not on Insiders or whatever and I am certainly not going to be a test-goat for some kind of preview of an update!
    I think it’s really weird that updates are offered in their preview status!

  • Martin 0

    This update breaks our application, where to report this?

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