CVE-2026-53551
Severity CVSS v4.0:
MEDIUM
Type:
CWE-20
Input Validation
Publication date:
31/07/2026
Last modified:
31/07/2026
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.
Impact
Base Score 4.0
6.90
Severity 4.0
MEDIUM
References to Advisories, Solutions, and Tools
- 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