CVE-2026-55784 free5gc CVE debrief

Who should care

Defenders responsible for 5G core network security, particularly those managing free5GC AUSF components, should assess exposure and prioritize verification and mitigation. This includes operators, platform administrators, vulnerability management teams, and security teams who need to verify configurations, monitor for unusual patterns, and implement rate limiting to prevent such attacks. They should also review compensating controls for exposed systems and

Why it matters

This vulnerability allows an attacker to cause authentication denial of service in free5GC AUSF components by exploiting concurrent authentication request handling. Defenders should prioritize verifying and updating configurations, monitoring for unusual patterns, and implementing rate limiting to prevent such attacks.

• Denial of authentication services to subscribers due to concurrent authentication request floods
• Potential for authentication context overwrite and verification failures
• Need for verification of free5GC AUSF component configurations and mitigation of concurrent request vulnerabilities

Technical summary

The AUSF component in free5GC stores per-subscriber authentication state in a global sync.Map named AUSFContext.UePool. An attacker with access to the AUSF SBI/N12 interface can send concurrent POST /nausf-auth/v1/ue-authentications requests for the same target SUPI, causing all attempts to share one logical authentication context URL while K_aut, XRES, and EapID are repeatedly overwritten. This issue affects the AUSF component, which stores per-subscriber authentication state in a global sync.Map. A valid EAP-AKA' response for an earlier challenge is then checked against the latest context, causing AT_MAC verification to fail and denying authentication to the selected subscriber while the request flood

Defensive priority

Defenders should prioritize verifying and updating free5GC AUSF component configurations to prevent concurrent authentication request floods, and monitor for unusual authentication denial patterns.

Recommended defensive actions

• Verify and update free5GC AUSF component configurations to prevent concurrent authentication request floods
• Monitor for unusual authentication denial patterns
• Review and implement rate limiting on AUSF SBI/N12 interface
• Confirm whether affected product deployments exist in managed environments and assign an owner for follow-up
• 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

Evidence notes

The CVE record and NVD entry provide details on the vulnerability, including its description, CVSS score, and affected vendor. However, no fixed version is available as of this review. Affected deployments should verify configurations and assess exposure. The vulnerability impacts free5GC AUSF components, allowing an attacker to cause authentication denial of service by exploiting concurrent authentication request handling. Defenders should prioritize verifying and updating configurations, monitoring for unusual patterns, and review

Sources and references

Methodology and review provenance

AI-assisted synthesis based on stored public vulnerability evidence. System validation, approval state, and publication status do not by themselves establish human review of this revision. PatchSiren helps prioritize defensive review and does not prove exposure or remediation on any system.