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HIGH

CVE-2023-37276

CVSS v3

7.5

HIGH

EPSS Score

1.3 %

exploit probability, as of 2026-10-18

CISA KEV

No

known exploited

Exploitation

—

SSVC status

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Affected and fixed versions

Packages from OSV.dev and products from the vendors' CSAF advisories.

version not verifiedVersions not verified: read as OSV.dev and the vendors publish them, not checked against each vendor's release list.

Packages

  • aiohttpPyPIall versions · fixed in 3.8.5

Vendor advisories

  • CVE-2023-37276 Red Hat Product Security7 products fixed · 4 known affected

    python-aiohttp: HTTP request smuggling via llhttp HTTP request parser

    python-aiohttp as a component of Red Hat Ansible Automation Platform 1.2 · python-aiohttp as a component of Red Hat Ansible Automation Platform 2 · python-aiohttp as a component of Red Hat OpenShift Data Science (RHODS)

  • RHSA-2024:2010 Red Hat Product Security4 products fixed

    Red Hat Security Advisory: Satellite 6.15.0 release

  • RHSA-2024:1878 Red Hat Product Security3 products fixed

    Red Hat Security Advisory: RHUI 4.8 Release - Security Updates, Bug Fixes, and Enhancements

Full record on NVD

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.

Technical details

Published
2023-07-19

Frequently asked questions

What is CVE-2023-37276?

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.

Is CVE-2023-37276 actively exploited?

Active exploitation of CVE-2023-37276 has not been confirmed. Its EPSS score was 1.3% on 2026-10-18, the estimated probability of exploitation in the next 30 days.

What is the CVSS score for CVE-2023-37276?

CVE-2023-37276 has a CVSS v3 base score of 7.5 (HIGH severity).

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