Auth bypass in Free5gc
CVE-2026-42083
free5GC is an open-source implementation of the 5G core network. Prior to 4.2.2, PCF Npcf_SMPolicyControl missing authentication middleware allows unauthenticated access to SM policy handlers and disclosure of subscriber SUPI. In NewServer(), the smPolicyGroup route group is created and routes are applied without attaching the router authorization middleware. In contrast, other PCF service groups such as Npcf_PolicyAuthorization do attach RouterAuthorizationCheck before route registration. Because the middleware is missing, requests to the /npcf-smpolicycontrol/v1/sm-policies, /npcf-smpolicycontrol/v1/sm-policies/{smPolicyId}, /npcf-smpolicycontrol/v1/sm-policies/{smPolicyId}/update, and /npcf-smpolicycontrol/v1/sm-policies/{smPolicyId}/delete endpoints can reach business logic even when no valid OAuth token is provided. This vulnerability is fixed in 4.2.2.
Vulnerability class: Broken Access Control
Published · last modified .
CVSS v3 metric
CVSS v3 base score 8.2 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:L/A:N.
EPSS exploit prediction
EPSS: 0.005 (43.5th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 44th percentile — 43.5% 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-6rgm-gr97-x3j5 (Issue Tracking, Vendor Advisory)
- github.com/free5gc/free5gc/issues/844 (Exploit, Issue Tracking)
- github.com/free5gc/pcf/pull/63 (Patch, Issue Tracking)
- github.com/free5gc/pcf/commit/8c4d457cdf58bb239ee30e88c56b370b22073964 (Patch)
Frequently asked questions
- What is CVE-2026-42083?
- CVE-2026-42083 is a high-severity vulnerability in Free5gc, classified under Missing Authorization. CVSS score: 8.2/10. Published 2026-05-27.
- How severe is CVE-2026-42083?
- High severity. CVSS v3 base score is 8.2 out of 10.