IMPORTANT

This update was originally released in the Security and Quality Rollup that’s dated January 23, 2024.  This update is included in the Security and Quality Rollup that’s dated February 13, 2024.  There is no change to this update with this release on February 13, 2024.  If you have previously installed this update no action is needed.

Release Date:February 13, 2024

Version: .NET Framework 3.5 and 4.8.1

The January 23, 2024 update for Windows 11, version 22H2 and Windows 11, version 23H2 includes security and cumulative reliability improvements in .NET Framework 3.5 and 4.8.1. 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

There are no new security improvements in this release. This update is cumulative and contains all previously released security improvements.

Quality and Reliability Improvements

There are no new Quality and Reliability Improvements in this update.

ASP.NET

- Addresses an issue with "System.ArgumentException: Illegal characters in path" in some ASP.Net MVC requests.

.NET Libraries

- Addresses an issue where version of the OSS zlib library is out of date.

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

Go to Settings > Update & Security > Windows Update. In the Optional updates available area, you’ll find the link to download and install the update.

Windows Update for Business

Yes

Go to Settings > Update & Security > Windows Update. In the Optional updates available area, you’ll find the link to download and install the 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 update will automatically sync with WSUS if you configure Products and Classifications as follows:

Product: Windows 11, version 22H2 and Windows 11, version 23H2

Classification: Updates

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 4.8.1 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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