Revised 6/8/2021: On June 8th, 2021, this update was released to replace a previous update to address a “revocation server was offline” error that may occur during installation. If you’ve already installed a previous release of this update, no action is required.

Revised 4/15/2021: On April 13th, 2021, this update was released to replace a previous release of this some updates. See known issues section for more details. If you’ve already installed a previous release of an affected update, no action is required.

Today, we are releasing the February 2021 Security and Quality Rollup Updates for .NET Framework.

Security

CVE-2021-24111– .NET Framework Denial of Service Vulnerability

This security update addresses a denial of service vulnerability in .NET Framework. For more information please see CVE-2021-24111.

Quality and Reliability

This release contains the following quality and reliability improvements.

ASP.NET

• Addresses an issue where after installing the update released on October 20th, some ASP.Net applications fail during precompilation – likely with a message that contains the words “Error ASPCONFIG.”

CLR¹

• Improves the reliability of automatic Native Image generation task.

WPF²

• Addresses a hang when scrolling to the end of a TreeView, when layout rounding is enabled and DPI scaling is not 100%.

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

Known issues in this update

Exception Info: System.NullReferenceException at System.Windows.Interop.HwndMouseInputProvider.HasCustomChrome(System.Windows.Interop.HwndSource, RECT ByRef)
at System.Windows.Interop.HwndMouseInputProvider.GetEffectiveClientRect(IntPtr)
at System.Windows.Interop.HwndMouseInputProvider.PossiblyDeactivate(IntPtr, Boolean)
at System.Windows.Interop.HwndMouseInputProvider.Dispose()

<AppContextSwitchOverrides 
value="Switch.System.Windows.Interop.MouseInput.OptOutOfMoveToChromedWindowFix=true; 
Switch.System.Windows.Interop.MouseInput.DoNotOptOutOfMoveToChromedWindowFix=true " />

Getting the Update

The Security and Quality Rollup is available via Windows Update, Windows Server Update Services, and Microsoft Update Catalog. The Security Only Update is available via 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 and newer versions.

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

Previous Monthly Rollups

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

• .NET Framework January Security and Quality Rollup Update
• .NET Framework November 2020 Cumulative Update Preview for Windows 10 2004 and Windows Server, version 2004
• .NET Framework November 2020 Cumulative Update Preview
• .NET Framework November 2020 Security and Quality Rollup Updates