An elevation of privilege vulnerability exists in Microsoft Exchange Server. An attacker who successfully exploited this vulnerability could gain the same rights as a Domain Administrator.
Exploitation of this vulnerability requires Exchange Web Services (EWS) and Push Notifications to be enabled and in use in an affected environment. To exploit the vulnerability, an attacker would need to execute a man-in-the-middle attack to forward an authentication request to a Microsoft Active Directory domain controller, thereby facilitating gaining of increased privileges on the domain controller.
To address this vulnerability, Microsoft has evaluated the rights granted to Exchange Servers and Exchange Administrators in the identified scenarios and determined changes are possible which lower the permissions granted within an Active Directory domain. The actual permission changes will vary based upon the version of Exchange Server in use. Please see https://support.microsoft.com/kb/4490059 for more information.