Microsoft .NET Framework 1.1 SP1, 2.0 SP2, 3.0 SP2, 3.5, 3.5.1, 4, 4.5, 4.5.1, and 4.5.2 does not properly use a hash table for request data, which allows remote attackers to cause a denial of service (resource consumption and ASP.NET performance degradation) via crafted requests, aka ".NET Framework Denial of Service Vulnerability."
https://docs.microsoft.com/en-us/security-updates/securitybulletins/2014/ms14-053
http://www.securitytracker.com/id/1030819