CVE-2026-34525 — Improper Input Validation in Aiohttp

CWE-20 — Improper Input ValidationCWE-444 — HTTP Request Smuggling8 documents7 sources
Severity
6.3MEDIUMNVD
EPSS
0.1%
top 72.27%
CISA KEV
Not in KEV
Exploit
No known exploits
Affected products
2
Aio-libs AiohttpAiohttp
Timeline
PublishedApr 1

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.

CVSS vector

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

Affected Packages2 packages

▶PyPIaiohttp/aiohttp< 3.13.4
▶CVEListV5aio-libs/aiohttp< 3.13.4

🔴Vulnerability Details

4
GHSA
AIOHTTP accepts duplicate Host headers↗2026-04-01
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CVEList
AIOHTTP: Duplicate Host header accepted↗2026-04-01
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OSV
CVE-2026-34525: AIOHTTP is an asynchronous HTTP client/server framework for asyncio and Python↗2026-04-01
▶
OSV
AIOHTTP accepts duplicate Host headers↗2026-04-01
▶

📋Vendor Advisories

2
Red Hat
aiohttp: aiohttp: Security bypass via multiple Host headers↗2026-04-01
▶
Debian
CVE-2026-34525: python-aiohttp - AIOHTTP is an asynchronous HTTP client/server framework for asyncio and Python. ...↗2026
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🕵️Threat Intelligence

1
Wiz
CVE-2026-34525 Impact, Exploitability, and Mitigation Steps | Wiz↗
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CVE-2026-34525 — Improper Input Validation in Aiohttp | cvebase