The Remote Desktop ActiveX control in mstscax.dll in Microsoft Remote Desktop Connection Client 6.1 and 7.0 does not properly handle objects in memory, which allows remote attackers to execute arbitrary code via a web page that triggers access to a deleted object, and allows remote RDP servers to execute arbitrary code via unspecified vectors that trigger access to a deleted object, aka "RDP ActiveX Control Remote Code Execution Vulnerability."
https://oval.cisecurity.org/repository/search/definition/oval%3Aorg.mitre.oval%3Adef%3A16598
https://docs.microsoft.com/en-us/security-updates/securitybulletins/2013/ms13-029