Auth bypass in Free5gc
CVE-2026-44321
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 inbound OAuth2 middleware. The POST /upi/v1/upNodesLinks create-or-update handler accepts attacker-controlled JSON and passes it directly into UpNodesFromConfiguration(), which calls logger.InitLog.Fatalf(...) on several validation failures. One confirmed path is the UE-IP-pool overlap check: a single unauthenticated POST that adds a new UPF whose pool overlaps an existing UPF terminates the entire SMF process (docker ps shows Exited (1)), not just the goroutine. This vulnerability is fixed in 4.2.2.
Vulnerability class: Broken Authentication
Published · last modified .
CVSS v3 metric
CVSS v3 base score 7.5 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H.
EPSS exploit prediction
EPSS: 0.006 (46.9th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 47th percentile — 46.9% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.004 · newest: 0.006 · change: +0.002
Affected products
- Free5gc — versions < 4.2.2
Weakness classification (CWE)
References
- github.com/free5gc/free5gc/security/advisories/GHSA-44qj-cghf-9p97 (Exploit, Vendor Advisory)
- github.com/free5gc/free5gc/issues/906 (Exploit, Issue Tracking)
- github.com/free5gc/smf/pull/203 (Patch, Issue Tracking)
- github.com/free5gc/smf/commit/e0974e07ddab44a67d36a563cca383b2449e33e5 (Patch)
Frequently asked questions
- What is CVE-2026-44321?
- CVE-2026-44321 is a high-severity vulnerability in Free5gc, classified under Missing Authentication for Critical Function. CVSS score: 7.5/10. Published 2026-05-27.
- How severe is CVE-2026-44321?
- High severity. CVSS v3 base score is 7.5 out of 10.