GHSA-CMPJ-2X3G-M7G3 free5GC's NEF nnef-oam route group is unauthenticated; no-token requests reach the OAM handler

Summary free5GC's NEF mounts the nnef-oam route group without inbound OAuth2/bearer-token authorization. A network attacker who can reach NEF on the SBI can hit the OAM route with no Authorization header at all and the handler returns 200 OK. The current OAM handler is a stub that returns null, b...