Vulnerability Description
free5GC is an open-source implementation of the 5G core network. Prior to 1.4.5, the free5GC AUSF (Authentication Server Function) does not validate the supiOrSuci field in UE authentication requests. Null bytes (\x00) and other control characters pass through JSON parsing unchanged and are forwarded to the UDM in an unescaped URL path. This causes Go's net/url.Parse() to fail, returning HTTP 500 "System failure" and leaking internal stack traces. An unauthenticated attacker can trigger this at scale causing denial of service for all subscribers attempting authentication through the affected AUSF. This vulnerability is fixed in 1.4.5.
Related Weaknesses (CWE)
References
- https://github.com/free5gc/ausf/commit/bfc4a10094dbacbd862baa4686829f3fcc06ce1e
- https://github.com/free5gc/ausf/pull/61
- https://github.com/free5gc/ausf/releases/tag/v1.4.5
- https://github.com/free5gc/free5gc/issues/1048
- https://github.com/free5gc/free5gc/releases/tag/v4.2.2
- https://github.com/free5gc/free5gc/security/advisories/GHSA-qj55-47fp-p62j
- https://github.com/free5gc/free5gc/security/advisories/GHSA-qj55-47fp-p62j
FAQ
What is CVE-2026-53551?
CVE-2026-53551 is a documented vulnerability. free5GC is an open-source implementation of the 5G core network. Prior to 1.4.5, the free5GC AUSF (Authentication Server Function) does not validate the supiOrSuci field in UE authentication requests....
How severe is CVE-2026-53551?
CVSS scoring is not yet available for CVE-2026-53551. Check NVD for updates.
Is there a patch for CVE-2026-53551?
Check the references section above for vendor advisories and patch information. Review vendor security bulletins for remediation guidance.