This vulnerability allows attackers to execute arbitrary code on vulnerable installations of Microsoft's Remote Desktop Client. Authentication is not required to exploit this vulnerability.
The specific flaw exists within mstscax.dll when parsing packets from an RDP server. A design flaw in the client allows a malicious RDP server to write to arbitrary memory inside the connecting processes memory space. By hosting a malicious RDP server, an attacker can execute arbitrary code on any client that attempts to connect to it. Privileges gained depend on which user is running the client.