This version is a specific for .NET Framework 4.0. Please note that Microsoft has officially ended support for .NET Framework 4.0, 4.5, and 4.5.1. Users are strongly advised to upgrade to a supported version (4.8 or later) for security and compatibility reasons. Understanding .NET Framework 4.0.3019 (KB2600217) What is this version? Version 4.0.3019 is not a standalone release of the .NET Framework. It is the build number associated with Update KB2600217 , which was released on October 25, 2011 .