March 17, 2020-KB4550993 Update for .NET Framework 4.8 for Windows 10 version 1607 and Windows Server 2016

Applies to: .NET Framework

The March 17, 2020 update for Windows 10 version 1607 and Windows Server 2016 includes a reliability improvement in .NET 4.8.  Before you install this update, see the Prerequisites and Restart requirement sections.

Quality and reliability improvements


Addresses an issue when the hosting of a .NET Framework implemented COM server in a DllSurrogate (e.g. dllhost.exe) that is running elevated is unable to opt-out of a security mechanism put in place in .NET Framework 4.8. This fix respects the opt-out mechanism and permits the COM server the ability to properly activate. This update does nothing to change the behavior or robustness of .NET Framework 4.8 when the opt-out mechanism is not set.

1 Common Language Runtime (CLR)

How to obtain and install the update

Install this update

This update is availabe on the Microsoft Update Catalog website.

File information

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


To apply this update, you must have .NET Framework 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