August 10, 2021 - KB5004331 Cumulative 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, and Windows Version 21H1
The August 10, 2021 update for Windows 10, version 2004, Windows Server, version 2004, Windows 10, version 20H2, and Windows Server, version 20H2, and Windows Version 21H1 includes cumulative reliability improvements in .NET Framework 3.5 and 4.8. We recommend that you apply this update as part of your regular maintenance routines. Before you install this update, see the Prerequisites and Restart requirement sections.
There are no new security improvements in this release. This update is cumulative and contains all previously released security improvements.
Quality and reliability improvements
1 Common Language Runtime (CLR)
CLR - In scenarios with both high numbers of assemblies and high numbers of GC heaps, Server GC can encounter serious lock contention during generation 2 GCs. A config switch has been introduced as a workaround. It can either be enabled from a .config file:
Or by setting environment variable COMPLUS_GCStaticsNoLockto a non-zero value. If the config switch is not enabled, behavior is unchanged compared to previous versions.
Winforms - Addresses an issue where some Windows Forms applications that use ToolStrip controls with ToolStripControlHost, and run under UIA Accessibility Tools, could make Accessibility Tools unresponsive.
- Addresses a regression in the ComboBox item accessible object where Accessibility Tools was not able to distinguish between identical items in the ComboBox and was becoming unresponsive.
How to get this update
Install this update
Release Channel Available Next Step Windows Update and Microsoft Update Yes To download and install this update, go to Settings > Update & Security > Windows Update, and then select Check for updates. Microsoft Update Catalog Yes To get the standalone package for this update, go to the Microsoft Update Catalog website. Windows Server Update Services (WSUS) No You can import this update into WSUS manually. See the Microsoft Update Catalog for instructions.
For a list of the files that are provided in this update, download the file information for cumulative update.
To apply this update, you must have .NET Framework 3.5 or 4.8 installed.
You must restart the computer after you apply this update if any affected files are being used. We recommend that you exit all .NET Framework-based applications before you apply this update.
How to obtain help and support for this update
Known issues in this update
- Help for installing updates: Windows Update FAQ
- Protect yourself online and at home: Windows Security support
- Local support according to your country: International Support
Microsoft is not currently aware of any issues in this update.
Source: July 29, 2021-KB5004331 Cumulative Update Preview 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, and Windows Version 21H1
See also: .NET Framework July 2021 Cumulative Update Preview
Direct download links for KB5004331 MSU file from Microsoft Update Catalog:
Download KB5004331 MSU for Windows 10 v2004, v20H2, and v21H1 32-bit (x86) - 41.8 MB
Download KB5004331 MSU for Windows 10 v2004, v20H2, and v21H1 64-bit (x64) - 65.4 MB
Download KB5004331 MSU for Windows 10 v2004, v20H2, and v21H1 ARM64 - 41.8 MB