In this blog post we are going to discuss the details of a vulnerability in Windows Remote Desktop Services, which we recently uncovered. We reported the vulnerability to Microsoft in a coordinated disclosure process. Microsoft has released a fix in the latest security update and the vulnerability is now identified as CVE-2022-21893.
This vulnerability enables any standard unprivileged user connected to a remote machine via remote desktop to gain file system access to the client machines of other connected users, to view and modify clipboard data of other connected users, and to impersonate the identity of other users logged on to the machine using smart cards. This could lead to data privacy issues, lateral movement and privilege escalation.
The latest versions of Windows (client and server editions) are affected by this vulnerability, and it goes back at least to Windows Server 2012 R2, so we can say that the majority of Windows versions in use today are affected.