CVE-2026-34525

AIOHTTP: Duplicate Host header accepted

Published Apr 1, 2026 CVSS 4.0 · 6.3 Medium EPSS < 1% KEV · Not listed
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.

Remediation

No solution or workaround provided in the CVE record

Tracking

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Advisories

Source ID Title
Debian DLA Debian DLA DLA-4613-1 python-aiohttp security update
Debian DLA Debian DLA DLA-4876-1 python-aiohttp security update
Github GHSA Github GHSA GHSA-c427-h43c-vf67 AIOHTTP accepts duplicate Host headers
History
Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}

Type Values Removed Values Added
First Time appeared Aiohttp
Aiohttp aiohttp
CPEs cpe:2.3:a:aiohttp:aiohttp:*:*:*:*:*:*:*:*
Vendors & Products Aiohttp
Aiohttp aiohttp
Metrics cvssV3_1

{'score': 5.4, 'vector': 'CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:L/I:L/A:N'}

cvssV3_1

{'score': 5.3, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N'}

Type Values Removed Values Added
First Time appeared Aio-libs
Aio-libs aiohttp
Vendors & Products Aio-libs
Aio-libs aiohttp
Type Values Removed Values Added
References
Metrics threat_severity

None

cvssV3_1

{'score': 5.4, 'vector': 'CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:L/I:L/A:N'}

threat_severity

Moderate

Type Values Removed Values Added
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.
Title AIOHTTP: Duplicate Host header accepted
Weaknesses CWE-20
CWE-444
References
Metrics cvssV4_0

{'score': 6.3, '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'}

Weaknesses

Sources

Status
PUBLISHED
Assigner
GitHub_M
Published
Updated
Jun 23, 2026, 3:50 PM
Reserved
Mar 30, 2026, 4:03 PM
Status
Analyzed
Published
Apr 1, 2026, 9:17 PM
Modified
Oct 26, 2026, 9:10 PM
Severity
Moderate
Public date
Apr 1, 2026, 8:28 PM