CVE-2026-53551 Details
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.
A denial-of-service vulnerability has been identified in free5GC versions through 4.2.2, specifically within the Authentication Server Function (AUSF). The issue arises because the AUSF does not properly validate the 'supiOrSuci' field in user equipment (UE) authentication requests. This lack of validation allows null bytes and other control characters to be injected, which are then forwarded to the Unified Data Management (UDM) in an unescaped URL path. As a result, Go's 'net/url.Parse()' function fails, causing the AUSF to return an HTTP 500 error, while leaking internal stack traces. This vulnerability can be exploited by an unauthenticated attacker, disrupting authentication for all subscribers using the affected AUSF.
Users can upgrade to free5GC version 4.2.2 or later, where this vulnerability has been fixed.
Metrics
CVSS 4.0 Severity and Vector Strings:
VolerionCVSS 3.x Severity and Vector Strings:
No data available for CVSS Version 2.0 on this CVE.
Volerion
Assessed Jul 31, 2026CISA-ADP
Assessed Aug 3, 2026References to Advisories, Solutions, and Tools
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| URL | Source(s) | Tag(s) |
|---|---|---|
| https://github.com/free5gc/free5gc/security/advisories/GHSA-qj55-47fp-p62j | CISA-ADP | AdvisoryExploitRemedyVendor |
| https://github.com/free5gc/ausf/commit/bfc4a10094dbacbd862baa4686829f3fcc06ce1e | [email protected] | Source CodeVendor |
| https://github.com/free5gc/ausf/pull/61 | [email protected] | Source CodeVendor |
| https://github.com/free5gc/ausf/releases/tag/v1.4.5 | [email protected] | Release NotesVendor |
| https://github.com/free5gc/free5gc/issues/1048 | [email protected] | ExploitIssue TrackingTechnical DescriptionVendor |
| https://github.com/free5gc/free5gc/releases/tag/v4.2.2 | [email protected] | Release NotesVendor |
| https://github.com/free5gc/free5gc/security/advisories/GHSA-qj55-47fp-p62j | [email protected] | AdvisoryExploitRemedyVendor |
Weakness Enumeration
| CWE-ID | CWE Name | Source |
|---|---|---|
| CWE-20 | Improper Input Validation | [email protected] |
Affected Products
| Product | Versions |
|---|---|
| free5GC AUSF | <= 4.2.2 (semver) |
CPE
Remediation
| |
| free5GC | All versions |
CPE
Remediation
| |
Change History
2 change records found show changes
| Date | Action | Recorded By |
|---|---|---|
| Aug 3, 2026 | CVE Modified | CISA-ADP |
| Jul 31, 2026 | New CVE Received | [email protected] |