CVE-2026-44327 is a critical-severity (CVSS 10) Missing Authentication vulnerability in github.com/free5gc/nef. The records list no fixed version yet; check the vendor advisory below and apply the mitigations in the meantime.
free5GC: NEF nnef-oam route group is unauthenticated; no-token requests reach the OAM handler
Exploitation Status
Proof-of-concept exploit code exists
- CISA’s SSVC triage found public proof-of-concept exploit code for this CVE, though no confirmed active exploitation.
- CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.
Exploitation and automatability from CISA’s SSVC triage for CVE-2026-44327.
EPSS Exploitation Probability
Probability of exploitation in the next 30 days, from FIRST.org EPSS.
How urgent is this, really
Where this sits among everything scored
Real-World Exposure
github.com/free5gc/nefReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects Go packages — download data is not available via public APIs for these ecosystems.
Description
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 GETs 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 OKdirectly: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
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐹Go | github.com/free5gc/nef | all versions | No fix |
Affected Products
free5gcfree5gcDetection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for github.com/free5gc/nef, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Remediation status
The records we use list no patched version of github.com/free5gc/nef for CVE-2026-44327. Check the maintainer's advisory, and where your build allows, override or pin the dependency away from the vulnerable range.
Mitigate without a patch
Put an independent control in front of the weakness: restrict the affected endpoint or interface to trusted networks, require an additional authentication factor or proxy-level check, and invalidate existing sessions and credentials in case the flaw has already been used.
Frequently Asked Questions
Is CVE-2026-44327 in your dependencies?
Find it across Go, including transitive dependencies.