Ad hoc networks are vulnerable to various attacks. In addition, congestion caused by limited resources may occur at any time in the transmission of the packets at intermediate nodes. This paper proposes a dynamic congestion control method of the selection of a secure path. By estimating the average queue length at the nodes, the congestion level at present is detected. If the occurrence of the possible congestion is predicted, the network will select a new path where all nodes have been certified as trusted nodes, generating session keys in the TCP three-way handshake to prevent the denial of service attacks. Simulation results show that the new algorithm is superior to TCP Reno algorithm in terms of security, packets loss rate, throughput, and end-to-end delay.