Revised 1/15/2021:  Added known issues details for ASP.Net applications may not deliver cookieless tokens in the URI

Today, we are releasing the September 2020 Cumulative Update Preview Updates for .NET Framework.

Quality and Reliability

This release contains the following quality and reliability improvements.

ASP.NET

• Disabled resuse of AppPathModifier in ASP.Net control output.
• HttpCookie objects in the ASP.Net request context will be created with configured defaults for cookie flags instead instead of .Net.NET-style primitive defaults to match the behavior of `new HttpCookie(name)`.

CLR¹

• Added a CLR config variable Thread_AssignCpuGroups (1 by default) that can be set to 0 to disable automatic CPU group assignment done by the CLR for new threads created by Thread.Start() and thread pool threads, such that an app may do its own thread-spreading.
• Addressed a rare data corruption that can occur when using new API’s such as Unsafe.ByteOffset which are often used with the new Span types. The corruption could occur when a GC operation is performed while a thread is calling Unsafe.ByteOffset from inside of a loop.
• Addressed an issue regarding timers with very long due times ticking down much sooner than expected when the AppContext switch “Switch.System.Threading.UseNetCoreTimer” is enabled.

SQL

• Addressed a failure that sometimes occured when a user connected to one Azure SQL database, performed an enclave based operation, and then connected to another database under the same server that has the same Attestation URL and performed an enclave operation on the second server.

WCF²

• Addressed an issue with WCF services sometimes failing to start when starting multiple services concurrently.

Windows Forms

• Addressed a regression introduced in .NET Framework 4.8, where Control.AccessibleName, Control.AccessibleRole, and Control.AccessibleDescription properties stopped working for the following controls:Label,GroupBox,ToolStrip,ToolStripItems,StatusStrip,StatusStripItems,PropertyGrid,ProgressBar,ComboBox,MenuStrip,MenuItems,DataGridView.
• Addressed a regression in accessible name for combo box items for data bound combo boxes. .NET Framework 4.8 RTM started using type name instead of the value of the DisplayMember property as an accessible name, this fiximprovement uses the DisplayMember again.

¹ Common Language Runtime (CLR) ² Windows Communication Foundation (WCF)

<?xml version="1.0" encoding="utf-8" ?>
<configuration>
      <appSettings>
          <add key=”aspnet:DisableAppPathModifier” value=”true” />
     </appSettings>
</configuration>

<?xml version="1.0" encoding="utf-8" ?>
<configuration>
     <system.web>
          <anonymousidentification cookieless="UseCookies" />
          <sessionState cookieless="UseCookies" />
          <authentication>
               <forms cookieless="UseCookies" />
          </authentication>
     </system.web>
</configuration>

<?xml version="1.0" encoding="utf-8" ?>
<configuration>
     <appSettings>
          <add key="aspnet:DisableAppPathModifier" value="false" />
     </appSettings>
</configuration>

Getting the Update

The Cumulative Update Preview is available via Windows Update 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 and 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 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+ versions.

Previous Cumulative Updates

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

• .NET Framework September 2020 Security and Quality Rollup Updates
• .NET Framework September 3, 2020 Cumulative Update Preview for Windows 10 2004 and Windows Server, version 2004
• .NET Framework August 2020 Cumulative Update Preview
• .NET Framework August 2020 Security and Quality Rollup Updates