Memory Exhaustion Vulnerability in aiohttp Multipart Form Handling

Executive Summary

This vulnerability exists in the aiohttp framework, an asynchronous HTTP client/server framework for asyncio and Python. Prior to version 3.13.4, aiohttp would read the entire content of some multipart form fields into memory before enforcing the client_max_size limit. This means that large multipart form fields could be fully loaded into memory even if they exceeded the configured maximum size, potentially leading to excessive memory usage.

The issue was fixed in version 3.13.4 by changing the behavior to check the client_max_size limit before reading the entire field into memory.

Useful 0 Not Useful 0

Impact Analysis

This vulnerability can impact you by causing your application to consume excessive memory when processing multipart form data. Since aiohttp reads the entire field into memory before checking the size limit, an attacker could send very large multipart form fields that exceed the intended maximum size, potentially leading to increased memory usage, degraded performance, or even denial of service due to resource exhaustion.

Useful 0 Not Useful 0

Mitigation Strategies

To mitigate this vulnerability, upgrade aiohttp to version 3.13.4 or later, where the issue has been patched.

Useful 0 Not Useful 0