VulnerabilityAnalyzed

CVE-2026-34520

AIOHTTP is an asynchronous HTTP client/server framework for asyncio and Python.

LOW 2.7EPSS 0.46%

Does this matter?

Lower severity and a low EPSS score (0.46%). Track it; it rarely justifies an emergency change on its own.

Description

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 patched in version 3.13.4.

CVSS 4.0: 2.7 LOWCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N/E:U/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/M
EPSS: 0.46% probability · 39th percentile
CISA KEV: Not listed
Weakness: CWE-113
Affected: aiohttp/aiohttp
Source: security-advisories@github.com

References

https://github.com/aio-libs/aiohttp/commit/9370b9714a7a56003cacd31a9b4ae16eab109ba4Patch
https://github.com/aio-libs/aiohttp/releases/tag/v3.13.4Release Notes
https://github.com/aio-libs/aiohttp/security/advisories/GHSA-63hf-3vf5-4wqfPatch, Vendor Advisory

Source: NVD record, EPSS from FIRST.org, KEV from CISA. Refreshed daily.