Ella Core Vulnerable to UE Downlink Redirection via Forged PDUSessionResourceSetupResponse

Summary

A radio with a valid NG Setup can send a forged PDUSessionResourceSetupResponse carrying any UE's AMF-UE-NGAP-ID. Ella Core does not verify the message arrived on the SCTP association bound to that UE's logical NG-connection, then creates a GTP tunnel towards that radio.

Impact

Downlink user-plane traffic for the targeted UE is redirected to the attacker's radio.

Fix

UE context lookups are now scoped to the sending radio's SCTP association.