PatchSiren cyber security CVE debrief
CVE-2026-53551 free5gc CVE debrief
The free5GC AUSF component does not validate the supiOrSuci field in UE authentication requests, allowing null bytes and control characters to pass through JSON parsing. This causes a failure in Go's net/url.Parse(), resulting in an HTTP 500 error and leaked internal stack traces. An unauthenticated attacker can trigger this vulnerability at scale, causing denial of service for all subscribers attempting authentication through the affected AUSF. The vulnerability is fixed in version 1.4.5. Organizations should verify and apply the patch. The CVE record was published on 2026-07-31T20:16:51.697Z and has not been modified since then. Evidence from official CVE and NVD sources; vulnerability in free5GC AUSF component. Limited detail on affected scope and potential impact. To address this vulnerability, organizations should prioritize verification and application of the patch (version 1.4.5) as a critical step in mitigating the risk of denial of service. Additionally, reviewing authentication requests for suspicious activity and implementing compensating controls can help reduce the risk until the patch is applied. It is also essential to track exceptions, retest remediated assets, and close the item only after evidence is documented. The debrief aims to provide an executive overview covering the affected product or component, vulnerability class, likely operational impact, source-confidence limits, and review context.
- Vendor
- free5gc
- Product
- Unknown
- CVSS
- MEDIUM 6.9
- CISA KEV
- Not listed in stored evidence
- Original CVE published
- 2026-07-31
- Original CVE updated
- 2026-07-31
- Advisory published
- 2026-07-31
- Advisory updated
- 2026-07-31
Who should care
Organizations using free5GC AUSF component; security teams responsible for 5G core network infrastructure; operators and platforms using the affected component; vulnerability management teams; and security teams responsible for authentication and authorization processes.
Technical summary
The free5GC AUSF component does not validate the supiOrSuci field in UE authentication requests, allowing null bytes and control characters to pass through JSON parsing. This causes a failure in Go's net/url.Parse(), resulting in an HTTP 500 error and leaked internal stack traces. An unauthenticated attacker can trigger this vulnerability at scale, causing denial of service for all subscribers attempting authentication through the affected AUSF. The vulnerability is fixed in version 1.4.5.
Defensive priority
Medium priority due to potential for denial of service; verify and apply patch 1.4.5.
Recommended defensive actions
- Verify and apply patch 1.4.5
- Monitor authentication requests for suspicious activity
- Implement compensating controls for authentication and authorization
- Review the supplied official advisory or CVE record to validate affected scope, severity, and vendor guidance
- Plan vendor-supported updates or mitigations through normal change control where exposure is confirmed
- Check relevant monitoring, detection, and logs for exposed assets that need extra review
- Track exceptions, retest remediated assets, and close the item only after evidence is documented
Evidence notes
The free5GC AUSF component does not validate the supiOrSuci field in UE authentication requests, allowing null bytes and control characters to pass through JSON parsing. This causes a failure in Go's net/url.Parse(), resulting in an HTTP 500 error and leaked internal stack traces. An unauthenticated attacker can trigger this vulnerability at scale, causing denial of service for all subscribers attempting authentication through the affected AUSF. Evidence from official CVE and NVD sources; vulnerability in free5GC AUSF component. Limited detail on affected scope and potential impact. The vulnerability is fixed in version 1.4.5. Organizations should verify and apply the patch. The CVE record was published on 2026-07-31T20:16:51.697Z and has not been modified since then.
Official resources
AI-assisted PatchSiren debrief based on the supplied source corpus. The CVE record was published on 2026-07-31T20:16:51.697Z and has not been modified since then.