Microsoft .NET Framework 2.0 SP2, 3.5, 3.5.1, 4, 4.5, 4.5.1, and 4.5.2 allows remote attackers to cause a denial of service (recursion and performance degradation) via crafted encrypted data in an XML document, aka ".NET XML Decryption Denial of Service Vulnerability."
https://docs.microsoft.com/en-us/security-updates/securitybulletins/2015/ms15-048