Auth bypass in Free5gc
CVE-2026-44327
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.
Vulnerability class: Broken Authentication
Published · last modified .
CVSS v3 metric
CVSS v3 base score 10.0 (Critical). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:H/A:H.
EPSS exploit prediction
EPSS: 0.005 (42.5th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 43rd percentile — 42.5% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.003 · newest: 0.005 · change: +0.002
Affected products
- Free5gc — versions < 4.2.2
Weakness classification (CWE)
References
- github.com/free5gc/free5gc/security/advisories/GHSA-cmpj-2x3g-m7g3 (Exploit, Vendor Advisory)
- github.com/free5gc/free5gc/issues/861 (Exploit, Issue Tracking)
- github.com/free5gc/nef/pull/23 (Patch, Issue Tracking)
Frequently asked questions
- What is CVE-2026-44327?
- CVE-2026-44327 is a critical-severity vulnerability in Free5gc, classified under Missing Authentication for Critical Function. CVSS score: 10.0/10. Published 2026-05-27.
- How severe is CVE-2026-44327?
- Critical severity. CVSS v3 base score is 10.0 out of 10.