AIOHTTP's C parser (llhttp) accepts null bytes and control characters in response header values - header injection/security bypass

緊急 9.1CVE-2026-34520 · GHSA-63hf-3vf5-4wqf · PYSEC-2026-2102 · 01/04/2026 公開 · 26/10/2026 更新

要点

CVE-2026-34520 は aiohttp, aiohttp (aiohttp) に影響する深刻度「緊急」 (CVSS 9.1) の脆弱性です。
今後30日間に悪用される確率（EPSS）：0.48%（全脆弱性の 41.3% より高い）。
対処：3.13.4 以降に更新してください。

パッケージ	影響を受けるバージョン	修正済みバージョン
aiohttp PyPI	`< 3.13.4`	`3.13.4`
aiohttp aiohttp	`< 3.13.4`	`3.13.4`

概要

Summary

The C parser (the default for most installs) accepted null bytes and control characters in request headers.

Impact

An attacker could send header values that are interpreted differently than expected due to the presence of control characters. For example, request.url.origin() may return a different value than the raw Host header, or what a reverse proxy interpreted it as., potentially resulting in some kind of security bypass.

Patch: https://github.com/aio-libs/aiohttp/commit/9370b9714a7a56003cacd31a9b4ae16eab109ba4

NVD の説明

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.