The Common Language Runtime (CLR) in Microsoft .NET Framework 2.0, 2.0 SP1, 2.0 SP2, 3.5, and 3.5 SP1, and Silverlight 2, does not properly handle interfaces, which allows remote attackers to execute arbitrary code via (1) a crafted XAML browser application (XBAP), (2) a crafted Silverlight application, (3) a crafted ASP.NET application, or (4) a crafted .NET Framework application, aka "Microsoft Silverlight and Microsoft .NET Framework CLR Vulnerability."
https://oval.cisecurity.org/repository/search/definition/oval%3Aorg.mitre.oval%3Adef%3A6510
https://docs.microsoft.com/en-us/security-updates/securitybulletins/2009/ms09-061