CVE-2025-53786: Microsoft Exchange Server Hybrid Deployment Elevation of Privilege Vulnerability

What privileges could be gained by an attacker who successfully exploited the vulnerability within the organization’s cloud environment?

In an Exchange hybrid deployment, an attacker who first gains administrative access to an on-premises Exchange server could potentially escalate privileges within the organization’s connected cloud environment without leaving easily detectable and auditable trace. This risk arises because Exchange Server and Exchange Online share the same service principal in hybrid configurations.