In the last two months I have worked on several SharePoint issues where we identified that the servers running SharePoint were still using .NET framework 4.5 or .NET framework 4.5.1 which are unsupported since around a year (supported ended January 12th, 2016 as announced in August 2014):
- Support Lifecycle for .NET 4.5: https://support.microsoft.com/en-us/lifecycle/search/16396
- Support Lifecycle for .NET 4.5.1: https://support.microsoft.com/en-us/lifecycle/search/17343
Currently only .NET 4.5.2, 4.6, 4.6.1 and 4.6.2 are supported:
- Support Lifecycle for .NET 4.5.2: https://support.microsoft.com/en-us/lifecycle/search/17694
- Support Lifecycle for .NET 4.6: https://support.microsoft.com/en-us/lifecycle/search/18324
- Support Lifecycle for .NET 4.6.1: https://support.microsoft.com/en-us/lifecycle/search/18573
- Support Lifecycle for .NET 4.6.2: https://support.microsoft.com/en-us/lifecycle/search/18571
Please ensure to verify that the servers in your environments use a supported .NET framework version.
Be aware that aside normal fixes also no security fixes will be released for .NET 4.5 and .NET 4.5.1 as these versions are out of support!
- Moving to the .NET Framework 4.5.2
- Lifecycle support policy FAQ—Microsoft .NET Framework
- Runtime Changes in the .NET Framework 4.5.2
- Detecting the .NET framework version installed on your machine (search for Detecting the .NET Framework)