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PYSEC-2026-1099

AIOHTTP's unicode processing of header values could cause parsing discrepancies

Quick fix

PYSEC-2026-1099 — aiohttp: upgrade to the fixed version with the command below.

pip install --upgrade 'aiohttp>=3.13.3'

Details

### Summary The Python HTTP parser may allow a request smuggling attack with the presence of non-ASCII characters.

### Impact If a pure Python version of aiohttp is installed (i.e. without the usual C extensions) or AIOHTTP_NO_EXTENSIONS is enabled, then an attacker may be able to execute a request smuggling attack to bypass certain firewalls or proxy protections.

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Patch: https://github.com/aio-libs/aiohttp/commit/32677f2adfd907420c078dda6b79225c6f4ebce0

Are you affected?

Enter the version of the package you're using.

Affected packages

PyPI/aiohttp

Introduced in: 0Fixed in: 3.13.3

Fixpip install --upgrade 'aiohttp>=3.13.3'

References

https://github.com/aio-libs/aiohttp/security/advisories/GHSA-69f9-5gxw-wvc2[WEB]
https://nvd.nist.gov/vuln/detail/CVE-2025-69224[ADVISORY]
https://github.com/aio-libs/aiohttp/commit/32677f2adfd907420c078dda6b79225c6f4ebce0[FIX]
https://github.com/aio-libs/aiohttp[PACKAGE]
https://pypi.org/project/aiohttp[PACKAGE]
https://github.com/advisories/GHSA-69f9-5gxw-wvc2[ADVISORY]