Vulnerability in Aio-libs Aiohttp

CVE-2026-34519

AIOHTTP is an asynchronous HTTP client/server framework for asyncio and Python. Prior to version 3.13.4, an attacker who controls the reason parameter when creating a Response may be able to inject extra headers or similar exploits. This i…

EPSS: 0.001 (17.0th percentile) — read the EPSS interpretation.

Affected products

Aio-libs Aiohttp — versions < 3.13.4

Weakness classification (CWE)

CWE-113 — HTTP Response Splitting

References

https://github.com/aio-libs/aiohttp/security/advisories/GHSA-mwh4-6h8g-pg8w (x_refsource_CONFIRM)
https://github.com/aio-libs/aiohttp/commit/53b35a2f8869c37a133e60bf1a82a1c01642ba2b (x_refsource_MISC)
https://github.com/aio-libs/aiohttp/releases/tag/v3.13.4 (x_refsource_MISC)