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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.
Cite this page
CVE-2023-37276. CVEDatabase.com. Retrieved 1 May 2026. https://cvedatabase.com/cve/CVE-2023-37276
Use CWE-444, Aiohttp vendor hub and Aiohttp product page to widen CVE-2023-37276 into its surrounding weakness, vendor, and product context.
Compare it with CVE-2026-22815, CVE-2026-34516 and CVE-2026-34515 for nearby disclosures in the same product family.