CVE-2024-30251 Overview
CVE-2024-30251 is a Denial of Service (DoS) vulnerability in aiohttp, an asynchronous HTTP client/server framework for asyncio and Python. The vulnerability allows an attacker to send a specially crafted POST request with multipart/form-data content type that causes the aiohttp server to enter an infinite loop, rendering it completely unresponsive to any further requests.
Critical Impact
A single malicious request can completely disable an aiohttp-based web service, causing total application unavailability with no user interaction required.
Affected Products
- aiohttp versions prior to 3.9.4
- Applications using aiohttp server with multipart form data handling
- Python asyncio-based web services leveraging the aiohttp framework
Discovery Timeline
- 2024-05-02 - CVE-2024-30251 published to NVD
- 2025-11-03 - Last updated in NVD database
Technical Details for CVE-2024-30251
Vulnerability Analysis
This vulnerability (CWE-835: Loop with Unreachable Exit Condition) exists in aiohttp's multipart form data parsing logic. When the server receives a specially crafted POST request with multipart/form-data content type, the parser enters an infinite loop condition where the exit criteria can never be satisfied. This is a classic algorithmic complexity attack where the attacker exploits improper boundary condition handling in the multipart parser.
The attack is particularly dangerous because it requires no authentication, can be executed remotely over the network, and completely halts all server functionality with just one request. The infinite loop consumes server resources indefinitely, preventing the processing of any legitimate requests until the service is manually restarted.
Root Cause
The root cause lies in improper handling of multipart form data boundaries within the aiohttp request parser. When malformed boundary delimiters or specially structured multipart content is sent to the server, the parsing loop fails to detect an exit condition, causing it to iterate indefinitely. The parser lacks proper validation checks to ensure that the loop will terminate under all input conditions.
Attack Vector
The attack vector is network-based and requires no privileges or user interaction. An attacker can exploit this vulnerability by sending a single HTTP POST request to any endpoint on the target aiohttp server that processes multipart/form-data requests. The attack can be executed remotely against any exposed aiohttp server instance.
The vulnerability is triggered during the processing of the malicious request, before any application-level logic is reached. This means that even properly secured endpoints with authentication are vulnerable if the server parses multipart data before authentication checks.
Detection Methods for CVE-2024-30251
Indicators of Compromise
- Sudden complete unresponsiveness of aiohttp-based web services
- Server process showing 100% CPU utilization with no request completion
- Accumulated pending connections with no responses being sent
- HTTP 503 or connection timeout errors reported by monitoring systems
Detection Strategies
- Monitor for anomalous multipart/form-data POST requests with unusual boundary values or malformed content structures
- Implement request timeout monitoring to detect requests that exceed normal processing times
- Track CPU utilization spikes on servers running aiohttp applications
- Set up health check endpoints with alerting on consecutive failures
Monitoring Recommendations
- Deploy application performance monitoring (APM) to track request processing times and identify stuck requests
- Configure network-level monitoring to detect POST requests to aiohttp servers with suspicious payload characteristics
- Implement automated service restart mechanisms with alerting for aiohttp processes that become unresponsive
How to Mitigate CVE-2024-30251
Immediate Actions Required
- Upgrade aiohttp to version 3.9.4 or later immediately
- Review all applications using aiohttp to identify vulnerable deployments
- Implement request timeout configurations at the reverse proxy or load balancer level as an additional defense layer
- Consider deploying Web Application Firewall (WAF) rules to filter suspicious multipart requests
Patch Information
The aiohttp project has released version 3.9.4 which addresses this vulnerability. Multiple commits have been published to fix the issue:
- Commit 7eecdff163ccf029fbb1ddc9de4169d4aaeb6597
- Commit cebe526b9c34dc3a3da9140409db63014bc4cf19
- Commit f21c6f2ca512a026ce7f0f6c6311f62d6a638866
For detailed patch instructions, refer to the GitHub Security Advisory GHSA-5m98-qgg9-wh84.
Workarounds
- Users unable to upgrade can manually apply the patches from the linked commits to their aiohttp installation
- Implement a reverse proxy (nginx, HAProxy) in front of aiohttp servers with strict request timeout limits
- Configure rate limiting on endpoints that accept multipart form data
- Restrict access to multipart form data endpoints to trusted sources where possible
# Upgrade aiohttp to patched version
pip install --upgrade aiohttp>=3.9.4
# Verify the installed version
pip show aiohttp | grep Version
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
