Release Date:April 9, 2024

Version: .NET Framework 3.5 and 4.8

The April 9, 2024 update for Windows 11, version 21H2 includes security and 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.

Summary

Security Improvements

CVE-2024-21409 - .NET Framework Remote Code Execution Vulnerability This security update addresses a remote code execution vulnerability detailed in CVE-2024-21409.

.NET Framework Defense in Depth Vulnerability This security update addresses an issue where version of the OSS zlib library is out of date.

.NET Framework Defense in Depth Vulnerability This security update addresses an issue in AIA fetching process.

Quality and Reliability Improvements

ASP.NET

- Addresses an issue with JavaScriptSerializer where after installing the January Security and Quality update there is a performance degradation.

CLR1

- Addresses an issue with thread pool recycled lists become unresponsive on multi-CPU-group computers.

1Common Language Runtime (CLR)

Additional information about this update

The following articles contain additional information about this update as it relates to individual product versions.

  • 5037037 Description of the Cumulative Update for .NET Framework 3.5, 4.8 and 4.8.1 for Windows 11, version 21H2 (KB5037037)

Known issues in this update

Microsoft is not currently aware of any issues in this update.

How to get this update

Install this update

Release Channel

Available

Next Step

Windows Update and Microsoft Update

Yes

None. This update will be downloaded and installed automatically from Windows Update.

Windows Update for Business

Yes

None. This update will be downloaded and installed automatically from Windows Update.

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 individual .NET Framework product update will be installed, as applicable, by applying the operating system update. For more information about operating system updates see additional information about this update section.

File information

For a list of the files that are provided in this update, download the file information for cumulative update.

Prerequisites

To apply this update, you must have .NET Framework 3.5 or 4.8 installed.

Restart requirement

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

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