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Release Date:
February 15, 2022

Version:
.NET Framework 3.5 and 4.8

The February 15, 2022 update for Microsoft server operating system version 21H2 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.

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

Winforms

- Addresses a leak of IRawElementProviderSimple objects which was introduced in .NET Framework 4.8. This is an opt-in fix, add the following compatibility switch to the app.config file in order to dispose the accessible objects:

<runtime>

              <!-- AppContextSwitchOverrides values are in the form of 'key1=true|false;key2=true|false  -->

              <AppContextSwitchOverrides value="Switch.System.Windows.Forms.DisconnectUiaProvidersOnWmDestroy=true"/>

       </runtime>

Note: that when the accessibility server application opts into this fix, the accessibility client will receive errors when accessing the disconnected provider. This is expected because the corresponding control window is destroyed. Previous behavior where the provider was returning information for destroyed controls was incorrect.

NET Libraries

- Addresses an issue when Ssl negotiation can hang indefinitely when client certificates are used when TLS 1.3 is negotiated. Before the change renegotiation (PostHandshakeAuthentiction) would fail and SslStream or HttpWebRequest would observe a timeout.

Known issues in this update

Symptom

If you installed KB5011258 and then this update, KB5011258 was uninstalled.

Workaround

Reinstall KB5011258 after installing this update.

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.

Windows Update for Business

No

None. These changes will be included in the next security update to this channel. For more information about Windows Update for Business go to the Windows Update for Business website.

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.

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

Known issues in this update

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

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