The Session Management Function (SMF) is a core 5G network control-plane component. It creates, updates, and tears down user sessions, and it coordinates with the User Plane Function (UPF) to install forwarding rules for subscriber traffic. In practice, the SMF decides how traffic should be routed, what policies apply, and when session state changes.
SMF matters because a mistake in its signaling logic can affect both availability and traffic integrity. If it accepts forged, malformed, or out-of-context control messages, an attacker may be able to confuse session state, trigger denial of service, or influence where user traffic is sent. Defenders harden SMF deployments by tightly segmenting PFCP interfaces, validating protocol state as well as message syntax, and monitoring for unusual session modification activity or forwarding-rule changes. In 5G attacks, the SMF is often the control-point that turns a signaling flaw into real traffic impact.