Preface: Input validation will be difficult if the environment contains different features. Even though software developer follow the guideline. Because it use http or https connection design , so it increase the difficulties!
Background: Citrix Workspace app consists of the Citrix Receiver core, HDX engine, the new embedded browser engine, files view and mobile app aggregation.
By default, Citrix Workspace Updates is disabled on the VDA. This includes RDS multi-user server machines, VDI and Remote PC Access machines.
Vulnerability details: Improper access control in Citrix Workspace app for Windows 1912 CU1 and 2006.1 causes privilege escalation and code execution when the automatic updater service is running. Official details are shown below the URL:
Observation: One of the possible methods – refer below connection method. If suspicious workstation installed Citrix workspace application. Attacker can use https or http connection to exploit SMB design weakness to compromise the Active Directory system. The concept can be found on attached diagram.
Remark: There is a design weakness happened on Citrix workspace application. Seems the input validation requires improvement.