The .NET Framework 4.5.1 RTM has been released and is available for download
The Microsoft .NET Framework 4.5.1 is a highly compatible, in-place update to the Microsoft .NET Framework 4 and the Microsoft .NET Framework 4.5. This version of the .NET Framework runs side-by-side with the .NET Framework 3.5 SP1 and earlier versions, but performs an in-place update for the .NET Framework 4 and the .NET Framework 4.5. The web installer is a small package that automatically determines and downloads only the components applicable for a particular platform.
Supported Operating Systems:
Windows 7 Service Pack 1, Windows 8, Windows Server 2008 R2 SP1, Windows Server 2008 Service Pack 2, Windows Server 2012, Windows Vista Service Pack 2