CVE-2026-44327 is a critical-severity (CVSS 10) Missing Authentication vulnerability in github.com/free5gc/nef. No vendor fix is recorded yet; mitigation options are listed below.
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
EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.
How urgent is this, really
CVE-2026-44327 plotted by exploitation likelihood (EPSS) against impact (CVSS). The shaded corner — EPSS 50%+ and CVSS 7.0+ — is where this CVE doesn't sit, though severity or exploitability alone can still warrant action.
Where this sits among everything scored
Of 378,156 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Real counts from FIRST.org, not a sample — log-scaled since the landscape is heavily right-skewed.
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 |
Detection & 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
No patched version of github.com/free5gc/nef has shipped for CVE-2026-44327 yet. Where your build allows, override or pin the dependency away from the vulnerable range, and apply any maintainer-recommended mitigation.
Mitigate without a patch
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 Security's impact-aware SCA analyses which vulnerable code paths your application actually calls, so a match like CVE-2026-44327 can be triaged on real exposure rather than presence alone.
Tailored to CVE-2026-44327. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is CVE-2026-44327 in your dependencies?
O3 Security finds CVE-2026-44327 across Go dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.