{"cve":"CVE-2023-37276","nvd":{"published":"2023-07-19T20:15:10.603","modified":"2026-06-17T06:07:52.237","status":"Modified","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.","cvss_v4":null,"cvss_v3":{"version":"3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N","score":7.5},"cwes":["CWE-444"],"references":["https://github.com/aio-libs/aiohttp/blob/v3.8.4/.gitmodules","https://github.com/aio-libs/aiohttp/commit/9337fb3f2ab2b5f38d7e98a194bde6f7e3d16c40","https://github.com/aio-libs/aiohttp/security/advisories/GHSA-45c4-8wx5-qw6w","https://hackerone.com/reports/2001873","https://github.com/aio-libs/aiohttp/blob/v3.8.4/.gitmodules"],"products":["aiohttp:aiohttp"],"source":"nvd","synced_at":"2026-10-19T21:38:35.729974749+00:00"},"epss":{"cve":"CVE-2023-37276","score":0.01337,"percentile":0.71231,"date":"2026-10-31"},"kev":null,"osv":[{"id":"GHSA-45c4-8wx5-qw6w","url":"https://osv.dev/vulnerability/GHSA-45c4-8wx5-qw6w","summary":"aiohttp.web.Application vulnerable to HTTP request smuggling via llhttp HTTP request parser","modified":"2026-09-10T03:49:42.592843584Z","packages":[{"ecosystem":"PyPI","name":"aiohttp","purl":"pkg:pypi/aiohttp","ranges":["<3.8.5"],"fixed":["3.8.5"]}]},{"id":"PYSEC-2023-120","url":"https://osv.dev/vulnerability/PYSEC-2023-120","summary":"aiohttp.web.Application vulnerable to HTTP request smuggling via llhttp HTTP request parser","modified":"2023-11-08T04:13:00.855432Z","packages":[{"ecosystem":"PyPI","name":"aiohttp","purl":"pkg:pypi/aiohttp","ranges":["<3.8.5"],"fixed":["3.8.5"]}]}],"attribution":["This product uses the NVD API but is not endorsed or certified by the NVD.","EPSS scores: FIRST Exploit Prediction Scoring System, https://www.first.org/epss","Known exploited vulnerabilities: CISA Known Exploited Vulnerabilities Catalog, https://www.cisa.gov/known-exploited-vulnerabilities-catalog","Package advisories: OSV (https://osv.dev), from the GitHub Advisory Database, PyPA, Go, RustSec and other ecosystem databases, under CC-BY 4.0 or CC0","CVE records: the CVE Program's CVE List (https://www.cve.org), under its terms of use (https://www.cve.org/Legal/TermsOfUse). CVE is a registered trademark of The MITRE Corporation; this product is not affiliated with the CVE Program."]}