[AMF] Issue during Concurrent UE Registration (#2839) #2876
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While they were continuing their fuzzy testing and developing PacketRusher, an unusual issue with the AMF was observed. The problem arises when a single Ethernet frame containing three bundled SCTP chunks is sent. This behavior is reproduced with PacketRusher when attempting to concurrently register two UEs with the same MSIN.
The expected behavior is that the PDU Session Establishment Accept is sent inside a DownlinkNASTransport to RAN UE NGAP ID 1. However, it is actually sent inside an InitialContextSetupRequest to RAN UE NGAP ID 2. The MAC of this NAS message is invalid for the Security Context of RAN UE NGAP ID 2 (probably valid for RAN UE NGAP ID 1)