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.
Attack Parameters
Attack Vector
Network
Can be exploited remotely
Attack Complexity
Low
Easy to exploit
Attack Requirements
None
No additional conditions
Privileges Required
None
No privileges needed
User Interaction
None
No user interaction needed
Impact Assessment
Confidentiality
None
No data leak
Integrity
None
No data modification
Availability
Low
Partial disruption
CVSS Vector v4.0
Weakness Type (CWE)
Vulnerable Products
free5gc:ausf
free5gc:free5gc
References 6
https://github.com/free5gc/ausf/commit/bfc4a10094dbacbd862baa4686829f3fcc06ce1e
security-advisories@github.com
https://github.com/free5gc/ausf/pull/61
security-advisories@github.com
https://github.com/free5gc/ausf/releases/tag/v1.4.5
security-advisories@github.com
https://github.com/free5gc/free5gc/issues/1048
security-advisories@github.com
https://github.com/free5gc/free5gc/releases/tag/v4.2.2
security-advisories@github.com
https://github.com/free5gc/free5gc/security/advisories/GHSA-qj55-47fp-p62j
security-advisories@github.com