CVE-2026-44320 free5GC: NEF nnef-callback route group is unauthenticated; forged callback requests are accepted into the processing path

free5GC is an open-source implementation of the 5G core network. Prior to 4.2.2, free5GC's NEF mounts the nnef-callback route group without inbound OAuth2/bearer-token authorization. A forged or arbitrary bearer token e.g. Authorization: Bearer not-a-real-token is enough to reach the SMF-callback...