My Splunk server says it is missing the Microsoft security patch KB951847, which is .Net 3.5 SP1. I have had a few problems with other apps when this .Net upgrade was installed. Are there versions of .Net that should not go on to a Windows Splunk installation?
Splunk does not use .NET on Windows, so you can update .NET as you wish.
I have not had any issues with any of the .Net releases concerning Splunk.