A remote code execution vulnerability exists in the Credential Security Support Provider protocol (CredSSP). An attacker who successfully exploited this vulnerability could relay user credentials and use them to execute code on the target system. CredSSP is an authentication provider which processes authentication requests for other applications; any application which depends on CredSSP for authentication may be vulnerable to this type of attack. As an example of how an attacker would exploit this vulnerability against Remote Desktop Protocol, the attacker would need to run a specially crafted application and perform a man-in-the-middle attack against a Remote Desktop Protocol session. An attacker could then install programs; view, change, or delete data; or create new accounts with full user rights. The security update addresses the vulnerability by correcting how Credential Security Support Provider protocol (CredSSP) validates requests during the authentication process. To be fully protected against this vulnerability users must enable Group Policy settings on their systems and update their Remote Desktop clients. The Group Policy settings are disabled by default to prevent connectivity problems and users must follow the instructions documented HERE to be fully protected.