CVE-2023-37276 aiohttp vulnerable to HTTP request smuggling
Attackers can smuggle HTTP requests in aiohttp servers, potentially bypassing security controls or accessing unauthorized data.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2023-37276?
CVE-2023-37276 is a medium-severity vulnerability in aio-libs aiohttp, published on 19 Jul 2023. 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. aiohttp v3.8.4 and earlier are bundled with llhttp v6.0.6. Vulnerable code is used by aiohttp for its HTTP request parser when available which is the default case when installing from a wheel. This vulnerability only affects users of aiohttp as an HTTP server (ie `aiohttp.Application`), you are not affected by this vulnerability if you are using aiohttp as an HTTP client library (ie `aiohttp.ClientSession`). Sending a crafted HTTP request will cause the server to misinterpret one of the HTTP header values leading to HTTP request smuggling. This issue has been addressed in version 3.8.5. Users are advised to upgrade. Users unable to upgrade can reinstall aiohttp using `AIOHTTP_NO_EXTENSIONS=1` as an environment variable to disable the llhttp HTTP request parser implementation. The pure Python implementation isn't vulnerable.
Weakness: CWE-444
Which versions are affected by CVE-2023-37276?
3 open source packages ship an affected version, including aiohttp. It affects 1 product.
| Package | Affected | Fixed in |
|---|---|---|
aiohttp PyPI | All versions | 3.8.5 |
aiohttp PyPI | All versions | 3.8.5 |
aiohttp PyPI | All versions | 3.8.5 |
Products include Aiohttp Aiohttp.
How do I fix CVE-2023-37276?
Upgrade aiohttp to 3.8.5 or later.
Is CVE-2023-37276 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2023-37276 exists.
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 CLSA-2025-1754007187, DEBIAN-CVE-2023-37276, GHSA-45c4-8wx5-qw6w, PYSEC-2023-120, UBUNTU-CVE-2023-37276.