CVE-2026-34525

AIOHTTP: Duplicate Host header accepted

State: Published
Severity: 6.3 Medium
Published: Apr 1, 2026
Updated: Jun 23, 2026
Reserved: Mar 30, 2026

Description

AIOHTTP is an asynchronous HTTP client/server framework for asyncio and Python. Prior to version 3.13.4, multiple Host headers were allowed in aiohttp. This issue has been patched in version 3.13.4.

Scores

CVSS	Score	Vector	Source
4.0	6.3 Medium	CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:N/VI:L/VA:N/SC:L/SI:L/SA:N	GitHub_M

Weaknesses

CWE-20 Improper Input Validation
CWE-444 Inconsistent Interpretation of HTTP Requests ('HTTP Request/Response Smuggling')

Affected Products

Product	Versions
aiohttpaio-libs	< 3.13.4Affected

References

https://github.com/aio-libs/aiohttp/security/advisories/GHSA-c427-h43c-vf67
https://github.com/aio-libs/aiohttp/commit/53e2e6fc58b89c6185be7820bd2c9f40216b3000
https://github.com/aio-libs/aiohttp/commit/e00ca3cca92c465c7913c4beb763a72da9ed8349
https://github.com/aio-libs/aiohttp/releases/tag/v3.13.4

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