Microsoft .NET Framework 4.8
The December 10, 2019 update for Windows 8.1, RT 8.1, and Server 2012 R2 includes cumulative reliability improvements in .NET 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.
- All updates for Windows 8.1, Windows RT 8.1, and Windows Server 2012 R2 require that update KB 2919355 is installed. We recommend that you install update KB 2919355 on your Windows 8.1-based, Windows RT 8.1-based, or Windows Server 2012 R2-based computer so that you receive updates in the future.
- If you install a language pack after you install this update, you must reinstall this update. Therefore, we recommend that you install any language packs that you need before you install this update. For more information, see Add language packs to Windows.
Quality and reliability improvements
ASP.NET now emits a SameSite cookie header when HttpCookie.SameSite value is "None" to accommodate upcoming changes to SameSite cookie handling in Chrome. As part of this change, FormsAuth and SessionState cookies are also issued with SameSite = 'Lax' instead of the previous default of 'None', though these values can be overridden in web.config. Applications that use these cookies across sites – or with iframes – may see a loss of functionality that will require configuration updates to remedy.
For more information, refer to: https://docs.microsoft.com/en-us/aspnet/samesite/system-web-samesite.
Addresses an issue where some Per-Monitor Aware WPF applications that host System-Aware or Unaware child-windows, and run on .NET 4.8, may occasionally encounter a crash with exceptionSystem.Collections.Generic.KeyNotFoundException.
Addresses an issue where some ClickOnce applications or applications creating the default AppDomain with a restricted permission set may observe application launch or application runtime failures, or unexpected behaviors. The observable issue was the System.AppDomainSetup.TargetFrameworkName is null, leading to any quirks enabling reverting back to .NET Framework 4.0 behaviors.
1 Windows Presentation Foundation (WPF)
2 Common Language Runtime (CLR)
Additional information about this update
- 4533097 Description of the Security and Quality Rollup for .NET Framework 3.5, 4.5.2, 4.6, 4.6.1, 4.6.2, 4.7, 4.7.1, 4.7.2, 4.8 for Windows 8.1, RT 8.1, and Windows Server 2012 R2 (KB4533097)
How to obtain and install the update
Method 1: Windows Update
This update is available through Windows Update. When you turn on automatic updating, this update will be downloaded and installed automatically. For more information about how to get security updates automatically, see Windows Update: FAQ.
Method 2: Microsoft Update Catalog
To get the standalone package for this update, go to the Microsoft Update Catalog website.
Method 3: Windows Software Update Services (WSUS)
On your WSUS server, follow these steps:
- Select Start, select Administrative Tools, and then select Microsoft Windows Server Update Services 3.0.
- Expand ComputerName, and then select Action.
- Select Import Updates.
- WSUS opens a browser window in which you may be prompted to install an ActiveX control. You must install the ActiveX control to continue.
- After the ActiveX control is installed, you see the Microsoft Update Catalog screen. Type 4533097 into the Search box, and then select Search.
- Locate the .NET Framework packages that match the operating systems, languages, and processors in your environment. Select Add to add them to your basket.
- After you select all the packages that you require, select View Basket.
- To import the packages to your WSUS server, select Import.
- After the packages are imported, select Close to return to WSUS.
The updates are now available for installation through WSUS.
To apply this update, you must have .NET Framework 4.8 installed.
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.
Update replacement information
Known Issues in this update
There are no known issues with this update, however, this update resolves a previous known issue. This patch includes improvements to resolve a known issue discussed in KB4519567 that occurs after applying the October Preview of Quality Rollup for .NET Framework 4.8. To resolve this issue, install update for .NET Framework 4.8 for Windows 8.1, RT 8.1, and Windows Server 2012 R2 KB4533004.