GHSA-3p28-73q7-45xp: free5GC's NEF 3gpp-traffic-influence API is unauthenticated; missing or forged bearer tokens can create, read, patch, and delete subscriptions
Summaryfree5GC's NEF mounts the `3gpp-traffic-influence` API without inbound OAuth2/bearer-token authorization. A network attacker who can reach NEF on the SBI can create, read, patch, and delete traffic-influence subscriptions either with no `Authorization` header at all, or with a forged bearer token (e.g. `Authorization: Bearer not-a-real-token`). This includes creating `AnyUeInd=true` subscriptions intended to affect group / any-UE traffic steering. The route group is also reachable even when the running config's `ServiceList` does not declare it, so operators who think they disabled the service via config are still exposed.This is the highest-impact NEF service exposure observed in the lab because it enables unauthenticated state changes on traffic-steering policy objects rather than read-only exposure.DetailsValidated against the NEF container in the official Docker compose lab.Source repo tag: `v4.2.1`Running Docker image: `free5gc/nef:v4.2.0`Runtime NEF commit: `5ce35eab`Docker validation date: 2026-03-11NEF advertises `OAuth2 setting receive from NRF: true`, and its `ServiceList` only declares `nnef-pfdmanagement` and `nnef-oam`. Despite that, the `3gpp-traffic-influence` route group is mounted and reachable with no inbound auth middleware.Code evidence (paths in `free5gc/nef`):Route group mounted without auth middleware: `NFs/nef/internal/sbi/server.go:48`CRUD routes exposed at `/:afID/subscriptions` and `/:afID/subscriptions/:subID`: `NFs/nef/internal/sbi/api_ti.go:13`POST allocates AF/subscription state and writes traffic-influence data: `NFs/nef/internal/sbi/processor/ti.go:50`PATCH looks up and updates the subscription, then calls UDR/PCF: `NFs/nef/internal/sbi/processor/ti.go:279`DELETE looks up and removes the subscription: `NFs/nef/internal/sbi/processor/ti.go:355`NEF context only exposes outbound token acquisition (`GetTokenCtx`); there is no inbound authorization path: `NFs/nef/internal/context/nef_context.go:153`Config validation only allows `nnef-pfdmanagement` and `nnef-oam`: `NFs/nef/pkg/factory/config.go:126`PoCReproduced end-to-end against the running NEF at `http://10.100.200.19:8000`.CREATE subscription with NO `Authorization` header at all -> `201 Created`:CREATE second subscription with FORGED bearer token -> `201 Created`:READ with forged token -> `200 OK`:PATCH with forged token -> `500 Query to UDR failed` (still reaches business logic, not 401/403, so auth bypass confirmed):DELETE with forged token -> `204 No Content`:NEF container logs (`docker logs nef`) show the requests reaching business handlers and returning success / 500-from-business codes (never 401/403):ImpactMissing inbound authentication (CWE-306) and authorization (CWE-862) on the highest-impact NEF SBI surface. Any party that can reach NEF on the SBI network can:Create attacker-controlled traffic-influence subscriptions (including `AnyUeInd=true` group/any-UE subscriptions), redirecting AF traffic to attacker-chosen DNAIs and routing endpoints via SMF/UPF.Read existing AF subscriptions, leaking traffic-steering policy data.Patch existing subscriptions, modifying live traffic-steering decisions for legitimate AFs.Delete subscriptions, denying service to legitimately provisioned traffic influence.The traffic-influence route group is also reachable even when the runtime `ServiceList` does not declare it, so operators relying on `ServiceList` to disable the service do not actually get that protection.Affected: free5gc v4.2.1.Upstream issue: https://github.com/free5gc/free5gc/issues/859
Upstream fix: https://github.com/free5gc/nef/pull/23
CVSS v3.1: 9.4