Title

The VPN Gateway must terminate all network connections associated with a communications session at the end of the session. (Cat III impact)

Discussion

Idle TCP sessions can be susceptible to unauthorized access and hijacking attacks. By default, routers do not continually test whether a previously connected TCP endpoint is still reachable. If one end of a TCP connection idles out or terminates abnormally, the opposite end of the connection may still believe the session is available. These “orphaned” sessions use up valuable router resources and can be hijacked by an attacker. To mitigate this risk, routers must be configured to send periodic keep alive messages to check that the remote end of a session is still connected. If the remote device fails to respond to the TCP keep alive message, the sending router will clear the connection and free resources allocated to the session.

Check Content

Verify the VPN Gateway terminates all network connections associated with a communications session at the end of the session. If the VPN Gateway does not terminate all network connections associated with a communications session at the end of the session, this is a finding.

Fix Text

Configure the VPN Gateway to terminate all network connections associated with a communications session at the end of the session.

Additional Identifiers

Rule ID: SV-207221r971530_rule

Vulnerability ID: V-207221

Group Title: SRG-NET-000213

Expert Comments

CCIs tied to check.

Controls tied to check. These are derived from the CCIs shown above.