CVE-2026-34520CRITICAL 9.1EPSS p36.4%

CVE-2026-34520CVE-2026-34520

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.

Scoring

CVSS 3.19.1 (CRITICAL)
VectorCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:H
EPSS0.46% probability of exploitation · percentile 36.4% · 2026-06-18T12:00:27Z
Published2026-04-01
Last modified2026-04-16

Underlying weaknesses· 1

CWE-113

References

  1. https://github.com/aio-libs/aiohttp/commit/9370b9714a7a56003cacd31a9b4ae16eab109ba4
  2. https://github.com/aio-libs/aiohttp/releases/tag/v3.13.4
  3. https://github.com/aio-libs/aiohttp/security/advisories/GHSA-63hf-3vf5-4wqf

1

TypeTargetConfidenceTier
WeaknessImproper Neutralization of CRLF Sequences in HTTP Headers ('HTTP Request/Response Splitting')cwe-1130%live

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Sourced from NVD + FIRST.org EPSS. Curated for EU compliance use cases by Adam Lundqvist, Founder at SQUR.