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

CLR₁

- 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:

<configuration>
  <runtime>
    <GCStaticsNoLock enabled="true"/>
  </runtime>
</configuration>

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.

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)

Yes

This update will automatically sync with WSUS if you configure Products and Classifications as follows:

Product: Windows 10, version 2004, Windows Server, version 2004, Windows 10, version 20H2, and Windows Server, version 20H2, and Windows Version 21H1

Classification: Updates