aiohttp.web.Application vulnerable to HTTP request smuggling via llhttp HTTP request parser
Impact
aiohttp v3.8.4 and earlier are bundled with llhttp v6.0.6 which is vulnerable to CVE-2023-30589. The 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).
Reproducer
from aiohttp import web
async def example(request: web.Request):
headers = dict(request.headers)
body = await request.content.read()
return web.Response(text=f"headers: {headers} body: {body}")
app = web.Application()
app.add_routes([web.post('/', example)])
web.run_app(app)Sending a crafted HTTP request will cause the server to misinterpret one of the HTTP header values leading to HTTP request smuggling.
$ printf "POST / HTTP/1.1\r\nHost: localhost:8080\r\nX-Abc: \rxTransfer-Encoding: chunked\r\n\r\n1\r\nA\r\n0\r\n\r\n" \
| nc localhost 8080
Expected output:
headers: {'Host': 'localhost:8080', 'X-Abc': '\rxTransfer-Encoding: chunked'} body: b''
Actual output (note that 'Transfer-Encoding: chunked' is an HTTP header now and body is treated differently)
headers: {'Host': 'localhost:8080', 'X-Abc': '', 'Transfer-Encoding': 'chunked'} body: b'A'Patches
Upgrade to the latest version of aiohttp to resolve this vulnerability. It has been fixed in v3.8.5: pip install aiohttp >= 3.8.5
Workarounds
If you aren't able to upgrade you 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 to request smuggling:
$ python -m pip uninstall --yes aiohttp
$ AIOHTTP_NO_EXTENSIONS=1 python -m pip install --no-binary=aiohttp --no-cache aiohttpReferences
Affected software
Click a technology to see all vulnerabilities affecting it.
| Platform | Package | Vulnerable versions | Fixed in |
|---|---|---|---|
| Python (PyPI) | aiohttp | < 3.8.5 | 3.8.5 |
References
- https://github.com/aio-libs/aiohttp/security/advisories/GHSA-45c4-8wx5-qw6w
- https://nvd.nist.gov/vuln/detail/CVE-2023-37276
- https://github.com/aio-libs/aiohttp
- https://hackerone.com/reports/2001873
- https://github.com/aio-libs/aiohttp/commit/9337fb3f2ab2b5f38d7e98a194bde6f7e3d16c40
- https://github.com/aio-libs/aiohttp/commit/9c13a52c21c23dfdb49ed89418d28a5b116d0681
- https://github.com/aio-libs/aiohttp/blob/v3.8.4/.gitmodules
- https://github.com/pypa/advisory-database/tree/main/vulns/aiohttp/PYSEC-2023-120.yaml
- CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N- Weakness (CWE)
CWE-444- Platform
- Python (PyPI)
- Package
aiohttp- Disclosed
- 20.07.2023
- Updated
- 11.10.2026 15:17
Sources and licenses
OSV / GitHub Advisory Database - PYSEC-2023-120 - PyPA Advisory Database; CC BY 4.0
OSV / GitHub Advisory Database - GHSA-45c4-8wx5-qw6w - CC BY 4.0
Vulnerability history: aiohttp
All published vulnerabilities of this package (Python (PyPI)), newest first. Shows whether this is a one-off slip or a package that needs watching.
- Total entries
- 55
- First → latest
- 02.2021 10.2026
- Without a fix
- 0
- Exploited in attacks
- 0
Severity breakdown
- High 7
- Medium 29
- Low 19
Disclosures per year
- 2021: 1
- 2022: 0
- 2023: 6
- 2024: 7
- 2025: 1
- 2026: 40
-
aiohttp.web.Application vulnerable to HTTP request smuggling via llhttp HTTP request parser this entry
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