The "XML Interface to Messaging, Scheduling, and Signaling" (XIMSS) protocol implementation in CommuniGate Pro (CGP) 6.2 suffers from a Missing XIMSS Protocol Validation attack that leads to an email spoofing attack, allowing a malicious authenticated attacker to send a message from any source email address. The attack uses an HTTP POST request to a /Session URI, and interchanges the XML From and To elements.