Microsoft Metadirectory Services (MMS) is a centralized metadirectory service that provides connectivity, management, and interoperability functions to help unify fragmented directory and database environments. It enables enterprises to link together disparate data repositories such as Exchange directory, Active Directory, third-party directory services, and proprietary databases, for the purpose of ensuring that the data in each is consistent, accurate, and can be centrally managed.

A flaw exists that could enable an unprivileged user to access and manipulate data within MMS that should, by design, only be accessible to MMS administrators.