Technical Information

Brief overview of the risk:
The vulnerabilities could allow remote code execution in the security context of the transcoding service on the Exchange server if a user previews a specially crafted file using Outlook Web App (OWA). The transcoding service in Exchange that is used for WebReady Document Viewing is running in the LocalService account. The LocalService account has minimum privileges on the local computer and presents anonymous credentials on the network.
Detailed Information on the risk:

Remote code execution vulnerabilities exist in Microsoft Exchange Server through the WebReady Document Viewing feature. These vulnerabilities could allow remote code execution as Local System if a user views a specially crafted file through Outlook Web Access in a browser. An attacker who successfully exploited the vulnerabilities could run code on the affected server, but only as LocalService. The LocalService account has minimum privileges on the local computer and presents anonymous credentials on the network.

Further information on this exploit is available at : MS12-058