CVE-2025-69229 AIOHTTP vulnerable to DoS through chunked messages
Attackers can cause denial of service in applications using AIOHTTP by sending excessive chunked messages, leading to high CPU usage.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2025-69229?
CVE-2025-69229 is a medium-severity denial of service vulnerability in aio-libs aiohttp, published on 5 Jan 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
AIOHTTP is an asynchronous HTTP client/server framework for asyncio and Python. In versions 3.13.2 and below, handling of chunked messages can result in excessive blocking CPU usage when receiving a large number of chunks. If an application makes use of the request.read() method in an endpoint, it may be possible for an attacker to cause the server to spend a moderate amount of blocking CPU time (e.g. 1 second) while processing the request. This could potentially lead to DoS as the server would be unable to handle other requests during that time. This issue is fixed in version 3.13.3.
Weakness: CWE-770
Which versions are affected by CVE-2025-69229?
3 open source packages ship an affected version, including aiohttp. It affects 1 product.
| Package | Affected | Fixed in |
|---|---|---|
aiohttp PyPI | All versions | 3.13.3 |
aiohttp PyPI | All versions | 3.13.3 |
aiohttp PyPI | All versions | 3.13.3 |
Products include Aiohttp Aiohttp.
How do I fix CVE-2025-69229?
Upgrade aiohttp to 3.13.3 or later.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
Is CVE-2025-69229 being exploited?
There is no known exploitation of CVE-2025-69229 in the wild and no public exploit code.
Other vulnerabilities in aio-libs aiohttp
- CVE-2024-52303 aiohttp memory leak when middleware is enabled when requesting a resource with a non-allowed method
- CVE-2025-69223 AIOHTTP's HTTP Parser auto_decompress feature is vulnerable to zip bomb
- CVE-2024-30251 Denial of service when trying to parse malformed POST requests in aiohttp
- CVE-2023-49081 aiohttp's ClientSession is vulnerable to CRLF injection via version
- CVE-2026-22815 AIOHTTP: Uncapped memory usage possible through aiohttp allowing unlimited trailer headers
Sources
Also known as AZL-73512, AZL-73535, CLEANSTART-2026-CB45865, CLEANSTART-2026-SC74702, DEBIAN-CVE-2025-69229, ECHO-b126-93f5-659c and 6 more.