free5GC: NEF nnef-oam route group is unauthenticated; no-token requests reach the OAM handler

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No collected risk observation for these identifiers. This does not establish absence of exploitation or a zero probability.

free5GC is an open-source implementation of the 5G core network. Prior to 4.2.2, 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, but the structural defect is route-group-scoped: the entire OAM route group has no inbound auth middleware, so every future OAM operation added to this group inherits the missing auth boundary by default. This vulnerability is fixed in 4.2.2.

Source published

27 May 2026 15:40:41 UTC

Source modified

28 May 2026 14:40:53 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 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, but the structural defect is route-group-scoped: the entire OAM route group has no inbound auth middleware, so every future OAM operation added to this group inherits the missing auth boundary by default. This vulnerability is fixed in 4.2.2.

Source published

May 27, 2026, 3:40:41 PM (timezone not stated)

Source modified

May 28, 2026, 2:40:53 PM (timezone not stated)

Observed here

9 Nov 2026 11:03:51 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 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, but the structural defect is route-group-scoped: the entire OAM route group has no inbound auth middleware, so every future OAM operation added to this group inherits the missing auth boundary by default. 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

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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: 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 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`, but the structural defect is route-group-scoped: the entire OAM route group has no inbound auth middleware, so every future OAM operation added to this group inherits the missing auth boundary by default. Same root cause as the NEF traffic-influence and PFD-management findings. ### 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`, yet the OAM route group is mounted without any inbound auth middleware and answers unauthenticated `GET`s with `200 OK`. Code evidence (paths in `free5gc/nef`): - OAM route group mounted without auth middleware: `NFs/nef/internal/sbi/server.go:60` - OAM route exposed at `/`: `NFs/nef/internal/sbi/api_oam.go:9` - OAM processor returns `200 OK` directly: `NFs/nef/internal/sbi/processor/oam.go:9` - NEF context only exposes outbound token acquisition (`GetTokenCtx`); there is no inbound authorization path: `NFs/nef/internal/context/nef_context.go:153` ### PoC Reproduced against the running NEF at `http://10.100.200.19:8000` with no `Authorization` header: ``` curl -i http://10.100.200.19:8000/nnef-oam/v1/ ``` Observed output: ``` HTTP/1.1 200 OK null ``` NEF container logs (`docker logs nef`) show the request being served while OAuth is enabled: ``` [INFO][NEF][GIN] | 200 | GET | /nnef-oam/v1/ ``` ### Impact Missing inbound authentication (CWE-306) and authorization (CWE-862) on the NEF OAM SBI route group. Severity is scored against the OAM route group's intended capability surface (Operations / Administration / Maintenance), NOT against the current stub handler. The current handler is a stub that returns `null`, but the defect is route-group-scoped: there is no auth middleware on the group at all, so every future OAM operation added behind this group inherits the missing inbound auth boundary by default. Any party that can reach NEF on the SBI can: - Probe and enumerate the OAM route surface anonymously today. - Hit any future OAM-group endpoint (read, modify, restart-style operations) anonymously, because the auth boundary does not exist for this group. Operators who assume `OAuth2 setting receive from NRF: true` enforces inbound auth on NEF are wrong for this route group. Affected: free5gc v4.2.1. Upstream issue: https://github.com/free5gc/free5gc/issues/861 Upstream fix: https://github.com/free5gc/nef/pull/23

Source published

8 May 2026 22:59:22 UTC

Source modified

21 Jul 2026 13:57:54 UTC

Observed here

24 Oct 2026 13:19:41 UTC

Source terms

GitHub Advisory Database · CC-BY-4.0

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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 NEF nnef-oam route group is unauthenticated; no-token requests reach the OAM handler in github.com/free5gc/nef

Source published

25 Jun 2026 18:43:19 UTC

Source modified

25 Jun 2026 19:45:30 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.