Medium · published January 6, 2026
⚠️ Just a few chunked messages can bring your server to a crawl! AIOHTTP versions 3.13.2 and below have a sneaky CPU blocking issue that can lead to denial of service. 🔥 Think of your server as a busy restaurant kitchen. If too many orders come in at once, and the kitchen can only process them slowly, it blocks the chefs from making new meals — leaving hungry customers waiting. That's similar to the CPU being overwhelmed by chunked messages! If an attacker sends a flood of chunked requests, your server could spend crucial seconds processing each one, making it unable to handle legitimate requests. This could frustrate users and lead to downtime, which is absolutely devastating for any service!
Think of your server as a busy restaurant kitchen. If too many orders come in at once, and the kitchen can only process them slowly, it blocks the chefs from making new meals — leaving hungry customers waiting. That's similar to the CPU being overwhelmed by chunked messages! This vulnerability in AIOHTTP allows excessive CPU blocking when handling chunked messages due to the way the request.read() method processes large numbers of chunks, ultimately causing potential denial of service (DoS).
If an attacker sends a flood of chunked requests, your server could spend crucial seconds processing each one, making it unable to handle legitimate requests. This could frustrate users and lead to downtime, which is absolutely devastating for any service! Upgrade AIOHTTP to version 3.13.3 immediately to fix this issue. Additionally, monitor your server's performance and consider implementing rate limiting to mitigate potential abuse. Stay vigilant! You've got this! Fixing this is a breeze and will help keep your server running smoothly. 🛡️
| Product | Versions | Fixed in |
|---|---|---|
| aiohttp/aiohttp | < 3.13.3 | 3.13.3 |