Exchange 2013 CU16 and Exchange 2016 CU5, both of these Exchange versions now require .NET framework 4.6.2 on all supported OS platforms.

As mentioned in the release posts for Exchange 2013 CU16 and Exchange 2016 CU5, both of these Exchange versions now require .NET framework 4.6.2 on all supported OS platforms.  This post focusses on Windows 2012 and 2012 R2 installations, see note below about Windows 2016.

Exchange setup will check for the presence of the required .NET framework, if not present setup will halt.

This is also true when extending the AD Schema and preparing Active Directory.  If the machine where you are running the AD preparation commands does not have the required .NET framework, then the installer will log an error.   In the below example a Windows 2012 R2 domain controller, the Schema Master FMSO role holder, was used to initiate the PrepareSchema command.  This failed due to .NET not being updated on that server where the Exchange 2013 CU16 setup command was being executed:

setup.exe /IAcceptExchangeServerLicenseTerms /PrepareSchema

Let us say if you are running Exchange 2013 CU 10 or Exchange 2016 CU2, you cannot apply the latest CU to your current Exchange 2013 or Exchange 2016 directly. You will go with two steps pf Exchange CU update or three Steps including the .net fromwork update:

For Exchange 2013

1. Apply Exchange 2013 CU 15 on your Exchange 2013 CU10 first,

2. Apply .net framework 4.62 and its security updates

3. Apply the latest Exchange 2013 CU, says CU 17 or CU18 coming soon in late 09/2017

For Exchange 2016

1. Apply Exchange 2016 CU 4 on your Exchange 2016 CU2 server first,

2. Apply .net framework 4.62 and its security updates

3. Apply the latest Exchange 2016 CU, says CU 6 or CU7 coming soon in late 09/2017

Reference:

https://blogs.technet.microsoft.com/rmilne/2017/03/27/exchange-2013-cu16-and-exchange-2016-cu5-net-framework-requirement/