CVE-2025-69227 AIOHTTP vulnerable to DoS when bypassing asserts
Attackers can cause a denial of service via infinite loop in aiohttp when Python optimizations are enabled and POST bodies are processed.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2025-69227?
CVE-2025-69227 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. Versions 3.13.2 and below allow for an infinite loop to occur when assert statements are bypassed, resulting in a DoS attack when processing a POST body. If optimizations are enabled (-O or PYTHONOPTIMIZE=1), and the application includes a handler that uses the Request.post() method, then an attacker may be able to execute a DoS attack with a specially crafted message. This issue is fixed in version 3.13.3.
Weakness: CWE-835
Which versions are affected by CVE-2025-69227?
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-2025-69227?
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-2025-69227 being exploited?
There is no known exploitation of CVE-2025-69227 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-73506, AZL-73529, CLEANSTART-2026-LP35415, DEBIAN-CVE-2025-69227, ECHO-0555-db3f-4098, GHSA-jj3x-wxrx-4x23 and 5 more.