free5GC: SMF UPI management interface lacks auth middleware; unauthenticated topology read/write requests reach handlers

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free5GC is an open-source implementation of the 5G core network. Prior to 4.2.2, free5GC's SMF mounts the UPI management route group without OAuth2/bearer-token authorization middleware. A network attacker who can reach SMF on the SBI can hit UPI endpoints with no Authorization header at all, and the requests reach the SMF business handlers. In the running Docker lab this was directly demonstrated for read (GET /upi/v1/upNodesLinks), write (POST /upi/v1/upNodesLinks with attacker-controlled UP-node and link payload), and delete (DELETE /upi/v1/upNodesLinks/{nodeID}) operations. This vulnerability is fixed in 4.2.2.

Source published

27 May 2026 15:38:35 UTC

Source modified

28 May 2026 15:00:50 UTC

Observed here

23 Oct 2026 15:48:27 UTC

Source terms

CVE Program Terms of Use

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CVSS 3.1 · 10.0 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:H/A:H

free5GC is an open-source implementation of the 5G core network. Prior to 4.2.2, free5GC's SMF mounts the UPI management route group without OAuth2/bearer-token authorization middleware. A network attacker who can reach SMF on the SBI can hit UPI endpoints with no Authorization header at all, and the requests reach the SMF business handlers. In the running Docker lab this was directly demonstrated for read (GET /upi/v1/upNodesLinks), write (POST /upi/v1/upNodesLinks with attacker-controlled UP-node and link payload), and delete (DELETE /upi/v1/upNodesLinks/{nodeID}) operations. This vulnerability is fixed in 4.2.2.

Source published

May 27, 2026, 3:38:35 PM (timezone not stated)

Source modified

May 28, 2026, 3:00:50 PM (timezone not stated)

Observed here

9 Nov 2026 11:03:54 UTC

Source terms

ENISA EUVD · source terms and attribution apply

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This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: euvd · ENISA EUVD · source terms and attribution apply. Source text is retained; field grouping and change labels are provided by ChangeIntel.

EUVD CVSS 3.1 · 10.0 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:H/A:H

free5GC is an open-source implementation of the 5G core network. Prior to 4.2.2, free5GC's SMF mounts the UPI management route group without OAuth2/bearer-token authorization middleware. A network attacker who can reach SMF on the SBI can hit UPI endpoints with no Authorization header at all, and the requests reach the SMF business handlers. In the running Docker lab this was directly demonstrated for read (GET /upi/v1/upNodesLinks), write (POST /upi/v1/upNodesLinks with attacker-controlled UP-node and link payload), and delete (DELETE /upi/v1/upNodesLinks/{nodeID}) operations. This vulnerability is fixed in 4.2.2.

Source published

27 May 2026 17:16:38 UTC

Source modified

14 Oct 2026 20:10:00 UTC

Observed here

25 Oct 2026 10:17:21 UTC

Source terms

NIST NVD usage terms; underlying source attribution retained

Original source record · Cite this exact observation · Complete original publisher JSON

This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: nvd · NIST NVD usage terms; underlying source attribution retained. Source text is retained; field grouping and change labels are provided by ChangeIntel.

CVSS 3.1 · [email protected] · Secondary · 10.0 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:H/A:H

### Summary free5GC's SMF mounts the `UPI` management route group without OAuth2/bearer-token authorization middleware. A network attacker who can reach SMF on the SBI can hit `UPI` endpoints with no `Authorization` header at all, and the requests reach the SMF business handlers. In the running Docker lab this was directly demonstrated for read (`GET /upi/v1/upNodesLinks`), write (`POST /upi/v1/upNodesLinks` with attacker-controlled UP-node and link payload), and delete (`DELETE /upi/v1/upNodesLinks/{nodeID}`) operations. The defect is route-group-scoped: there is no inbound auth middleware on the UPI group at all, while a control comparison against the sibling `nsmf-oam` group on the same SMF instance shows OAM IS protected (no-token request returns `401 Unauthorized`). So this is not a global config gap -- it is specifically that the UPI group was mounted without the auth middleware that the OAM group has. ### Details Validated against the SMF container in the official Docker compose lab. - Source repo tag: `v4.2.1` - Running Docker image: `free5gc/smf:v4.2.0` - Docker validation date: 2026-03-13 Control comparison on the same SMF instance: - `GET /upi/v1/upNodesLinks` (no token) -> `200 OK` - `GET /nsmf-oam/v1/` (no token) -> `401 Unauthorized` This side-by-side proves OAuth2 middleware is wired in for `nsmf-oam` but not for `UPI` on the same process. Code evidence (paths in `free5gc/smf`): - UPI group mounted WITHOUT auth middleware: `NFs/smf/internal/sbi/server.go:76` - OAM group mounted WITH auth middleware (control): `NFs/smf/internal/sbi/server.go:95` - UPI business handlers (read / write / delete on `upNodesLinks`): - `NFs/smf/internal/sbi/api_upi.go:44` - `NFs/smf/internal/sbi/api_upi.go:60` - `NFs/smf/internal/sbi/api_upi.go:84` ### PoC Reproduced end-to-end against the running SMF at `http://10.100.200.6:8000`. 1. READ UP-nodes/links with NO `Authorization` header -> `200 OK`: ``` curl -i http://10.100.200.6:8000/upi/v1/upNodesLinks ``` 2. WRITE: POST attacker-controlled UPF node and link with NO `Authorization` header -> `200 OK`: ``` curl -i -X POST http://10.100.200.6:8000/upi/v1/upNodesLinks \ -H 'Content-Type: application/json' \ --data '{"links":[{"A":"gNB1","B":"UPF-POC-20260313","weight":1}],"upNodes":{"UPF-POC-20260313":{"type":"UPF","nodeID":"198.51.100.20","addr":"198.51.100.20","sNssaiUpfInfos":[{"sNssai":{"sst":1,"sd":"010203"},"dnnUpfInfoList":[{"dnn":"internet"}]}]}}}' ``` 3. DELETE with FORGED token -> `404 Not Found` from business logic (auth was bypassed; the 404 is a business response, not an auth rejection): ``` curl -i -X DELETE http://10.100.200.6:8000/upi/v1/upNodesLinks/UPF-POC-20260313 \ -H 'Authorization: Bearer not-a-real-token' ``` 4. CONTROL: same instance, sibling OAM route, no token -> `401 Unauthorized`: ``` curl -i http://10.100.200.6:8000/nsmf-oam/v1/ ``` SMF container logs (`docker logs smf`) confirm the side-by-side behavior: ``` [INFO][SMF][GIN] | 200 | GET | /upi/v1/upNodesLinks [INFO][SMF][GIN] | 401 | GET | /nsmf-oam/v1/ [INFO][SMF][GIN] | 404 | DELETE | /upi/v1/upNodesLinks/UPF-POC-20260313 [INFO][SMF][GIN] | 200 | POST | /upi/v1/upNodesLinks ``` ### Impact Missing inbound authentication (CWE-306) and authorization (CWE-862) on the SMF `UPI` SBI route group. Severity is scored against the route group's intended capability surface (UP-node and link topology management), which is realized by the demonstrated PoC: an unauthenticated network attacker can already today read SMF's view of the UP-plane topology, inject attacker-controlled UPF nodes and link entries, and target deletions of named entries. Any party that can reach SMF on the SBI can: - Read SMF's current UP-node and link topology view anonymously. - Inject attacker-controlled UPF entries (with attacker-chosen nodeID / addr / S-NSSAI / DNN), poisoning SMF's view of which UPFs serve which slices/DNNs and biasing subsequent UPF selection / PFCP path establishment for legitimate PDU sessions. - Issue topology delete operations against named UPF entries, denying or disrupting legitimate UPF participation in SMF's selection logic. The defect is route-group-scoped: there is no auth middleware on the UPI group at all, so every UPI endpoint inside this group inherits the missing inbound auth boundary, and the same-instance OAM control proves this is the UPI mount specifically (not a global SMF config issue). Affected: free5gc v4.2.1. Upstream issue: https://github.com/free5gc/free5gc/issues/887 Upstream fix: https://github.com/free5gc/smf/pull/197

Source published

8 May 2026 23:02:23 UTC

Source modified

8 Jun 2026 20:15:14 UTC

Observed here

24 Oct 2026 13:19:41 UTC

Source terms

GitHub Advisory Database · CC-BY-4.0

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This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: osv · GitHub Advisory Database · CC-BY-4.0. Source text is retained; field grouping and change labels are provided by ChangeIntel.

CVSS_V3 · CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:H/A:H

Publisher rating · CRITICAL

free5GC's SMF UPI management interface lacks auth middleware; unauthenticated topology read/write requests reach handlers in github.com/free5gc/smf

Source published

20 May 2026 19:07:16 UTC

Source modified

20 May 2026 19:30:13 UTC

Observed here

24 Oct 2026 13:19:41 UTC

Source terms

OSV · upstream source license applies

Original source record · Cite this exact observation · Complete original publisher JSON

This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: osv · OSV · upstream source license applies. Source text is retained; field grouping and change labels are provided by ChangeIntel.