Installing Microsoft .NET Framework 4.8 stalls at: "File security verification: All files were verified successfully. Installation progress:"

Problem

You’re attempting to upgrade an Exchange Server 2019 to Cumulative Update 7, which requires .NET Framework 4.8:

https://support.microsoft.com/en-ca/help/4571787/cumulative-update-7-for-exchange-server-2019

The prerequisites identifies that .NET Framework 4.8 is not present and provides a link to the following installer:

https://support.microsoft.com/en-us/help/4503548/microsoft-net-framework-4-8-offline-installer-for-windows

The following is the offline installer:

Executing it on the Exchange server loads the installer but stays stuck at the following prompt:

File security verification:

All files were verified successfully.

Installation progress:

Solution

Before begin troubleshooting, review the current version of .NET Framework installed with the following PowerShell cmdlet:

PS C:\Windows\system32> Get-ItemProperty -Path "HKLM:SOFTWARE\Microsoft\NET Framework Setup\NDP\v4\Full" | Format-List

CBS : 1

Install : 1

InstallPath : C:\Windows\Microsoft.NET\Framework64\v4.0.30319\

Release : 461814

Servicing : 0

TargetVersion : 4.0.0

Version : 4.7.03190

PSPath : Microsoft.PowerShell.Core\Registry::HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\NET Framework

Setup\NDP\v4\Full

PSParentPath : Microsoft.PowerShell.Core\Registry::HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\NET Framework Setup\NDP\v4

PSChildName : Full

PSDrive : HKLM

PSProvider : Microsoft.PowerShell.Core\Registry

PS C:\Windows\system32>

This issue is one that I’ve come across multiple times in the past as demonstrated in one of my previous posts:

Installing .NET Framework 4.7.1 on Windows Server 2016 as a prerequisite for patching Exchange 2016 CU8 to CU12 remains stuck at: “File security verification: All files were verified successfully.”
http://terenceluk.blogspot.com/2019/04/installing-net-framework-471-on-windows_4.html

There are times when waiting 20 minutes or more will proceed with the install:

However, what I’ve found that the MSU from the Microsoft Update Catalog installs much faster:

https://www.catalog.update.microsoft.com/Search.aspx?q=4486153

Once installed, execute the following cmdlet again to verify that .NET Framework 4.8 is installed:

Get-ItemProperty -Path "HKLM:SOFTWARE\Microsoft\NET Framework Setup\NDP\v4\Full" | Format-List

Hope this helps anyone who may run into this issue as updating Exchange Server to a CU is usually performed after hours with limited time for troubleshooting.