.NET 4.5.2 Update on Exchange Servers?

Microsoft Windows Update is now offering the .NET Framework 4.5.2 update as an “Important” update to Windows computers.

• Microsoft .NET Framework 4.5.2 for Windows 8.1 and Windows Server 2012 R2 for x64-based Systems (KB2934520)
• Microsoft .NET Framework 4.5.2 for Windows Server 2008 R2 for x64-based Systems (KB2901983)

First of all, keep in mind that both of these updates require a restart. It’s also important to mention that .NET Framework 4.5.2 is only supported and recommended for Exchange 2013 CU7, but it is being offered as an Important update to all Windows servers.

When this update is installed on your Windows servers it will re-optimize all .NET assemblies on the server when it restarts. Perfmon shows ~99% of CPU resources are in use for about 15-20 minutes while this occurs.

We recommend putting servers into maintenance mode on the load balancer prior to updating them and re-enabling them once optimization completes!