This disclosure describes an approach to detect replay attacks while having multiple cores in a multi-core processor manage an established tunneling session. The tunneling session includes a number of flows. One of the cores is assigned to manage one of the flows, and another core is assigned to manage another of the flows. A replay attack over the tunneling session is inhibited by maintaining a flow-based sequence context at each of the flows, and the flow-based sequence context is maintained by the core that is managing the respective flow.