Microsoft Exchange Server cmdlet argument validation RCE

Successful exploitation allows arbitrary code execution on the vulnerable Exchange server with SYSTEM privileges. This gives an attacker full control over the affected server, including the ability to run commands, install tools, access or modify Exchange data and configuration, and use the server as a foothold for further privilege escalation and lateral movement within the enterprise. Because Exchange commonly operates with high trust and broad connectivity, compromise can materially increase the risk of wider domain or network compromise.

If immediate patching is not possible, reduce exposure by tightly restricting access to Exchange administrative interfaces and limiting assignment of the Exchange role required for Data Loss Prevention operations to only essential administrators. Monitor Exchange management, PowerShell, Windows process creation, and IIS logs for suspicious DLP policy creation, unusual Exchange Control Panel activity, and web worker processes spawning command interpreters or PowerShell. Review and remove unnecessary privileged Exchange role memberships and isolate or restrict access to vulnerable Exchange servers until updates can be applied.

Apply the Microsoft security update released for CVE-2020-16875. The update remediates the issue by correcting how Microsoft Exchange validates and handles cmdlet arguments. Organizations should ensure all affected Exchange Server installations are updated to the vendor-fixed build level and verify that patch deployment succeeded across all internet-facing and internally accessible Exchange systems.