{"uuid": "c47f6d9c-09e6-4f87-aeb3-75edc0b7ad7c", "vulnerability_lookup_origin": "1a89b78e-f703-45f3-bb86-59eb712668bd", "author": "9f56dd64-161d-43a6-b9c3-555944290a09", "vulnerability": "GHSA-qj55-47fp-p62j", "type": "seen", "source": "https://gist.github.com/alon710/0f09a6f6c7f9c253322faa348755ead8", "content": "# CVE-2026-53551: CVE-2026-53551: Improper Input Validation in free5GC Authentication Server Function (AUSF)\n\n> **CVSS Score:** 6.9\n> **Published:** 2026-07-31\n> **Full Report:** https://cvereports.com/reports/CVE-2026-53551\n\n## Summary\nImproper input validation of the supiOrSuci field in free5GC Authentication Server Function (AUSF) allows unauthenticated remote attackers to trigger an unhandled parsing exception, resulting in a Denial of Service (DoS) and internal stack trace exposure.\n\n## TL;DR\nA null-byte input validation bug in free5GC AUSF crashes the authentication flow, causing Denial of Service for connecting subscribers.\n\n## Exploit Status: POC\n\n## Technical Details\n\n- **CWE ID**: CWE-20\n- **Attack Vector**: Network (Unauthenticated)\n- **CVSS v4.0**: 6.9 (Medium)\n- **Impact**: Denial of Service (DoS)\n- **Exploit Status**: PoC available\n- **CISA KEV Status**: Not Listed\n\n## Affected Systems\n\n- free5gc\n- ausf\n- **ausf**: < 1.4.5 (Fixed in: `1.4.5`)\n- **free5gc**: < 4.2.2 (Fixed in: `4.2.2`)\n\n## Mitigation\n\n- Upgrade free5gc to 4.2.2 or higher\n- Upgrade AUSF to 1.4.5 or higher\n- Implement API Gateway string pattern restrictions\n- Isolate the AUSF SBI within a protected VLAN/subnetwork\n\n**Remediation Steps:**\n1. Verify currently running version of free5gc and the AUSF microservice\n2. Download and compile AUSF version 1.4.5 or pull the updated docker container image\n3. Apply the updated configurations and restart the AUSF service\n4. Validate that POST requests containing null bytes inside the supiOrSuci parameter are safely rejected with HTTP 400 Bad Request\n\n## References\n\n- [GitHub Security Advisory GHSA-qj55-47fp-p62j](https://github.com/free5gc/free5gc/security/advisories/GHSA-qj55-47fp-p62j)\n- [free5GC GitHub Issue 1048](https://github.com/free5gc/free5gc/issues/1048)\n\n\n---\n*Generated by [CVEReports](https://cvereports.com/reports/CVE-2026-53551) - Automated Vulnerability Intelligence*", "creation_timestamp": "2026-07-31T21:31:45.153161Z"}