Microsoft Exchange Server is prone to a security-bypass vulnerability. Attackers can exploit this issue to bypass certain security restrictions to perform unauthorized actions. This may aid in further attacks. Microsoft Exchange Server 2013 Cumulative Update 22 and prior versions are vulnerable.
Block external access at the network boundary, unless external parties require service.
Filter access to the affected computer at the network boundary if global access isn't needed. Restricting access to only trusted computers and networks might greatly reduce the likelihood of a successful exploit.
Run all software as a nonprivileged user with minimal access rights.
When possible, run all software as a user with minimal privileges and limited access to system resources. Use additional precautions such as restrictive environments to insulate software that may potentially handle malicious content.
Deploy network intrusion detection systems to monitor network traffic for malicious activity.
Deploy NIDS to detect and block attacks and anomalous activity such as requests containing suspicious URI sequences. Since the webserver may log such requests, review its logs regularly.
Currently, we are not aware of any vendor-supplied patches. If you feel we are in error or if you are aware of more recent information, please mail us at: email@example.com.