LOW

GHSA-mwh4-6h8g-pg8w

AIOHTTP has HTTP response splitting via \r in reason phrase

Details

### Summary

An attacker who controls the `reason` parameter when creating a `Response` may be able to inject extra headers or similar exploits.

### Impact

In the unlikely situation that an application allows untrusted data to be used in the response's `reason` parameter, then an attacker could manipulate the response to send something different from what the developer intended.

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Patch: https://github.com/aio-libs/aiohttp/commit/53b35a2f8869c37a133e60bf1a82a1c01642ba2b

Are you affected?

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Affected packages

PyPI / aiohttp

Introduced in: 0 Fixed in: 3.13.4

Fix pip install --upgrade 'aiohttp>=3.13.4'

References

https://github.com/aio-libs/aiohttp/security/advisories/GHSA-mwh4-6h8g-pg8w [WEB]
https://nvd.nist.gov/vuln/detail/CVE-2026-34519 [ADVISORY]
https://github.com/aio-libs/aiohttp/commit/53b35a2f8869c37a133e60bf1a82a1c01642ba2b [WEB]
https://github.com/aio-libs/aiohttp [PACKAGE]
https://github.com/aio-libs/aiohttp/releases/tag/v3.13.4 [WEB]