Vulnerability in Aio-libs Aiohttp

CVE-2026-34520

AIOHTTP is an asynchronous HTTP client/server framework for asyncio and Python. Prior to version 3.13.4, the C parser (the default for most installs) accepted null bytes and control characters in response headers. This issue has been patch…

EPSS: 0.001 (23.3th 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-63hf-3vf5-4wqf (x_refsource_CONFIRM)
https://github.com/aio-libs/aiohttp/commit/9370b9714a7a56003cacd31a9b4ae16eab109ba4 (x_refsource_MISC)
https://github.com/aio-libs/aiohttp/releases/tag/v3.13.4 (x_refsource_MISC)