CVE-2026-34525
AIOHTTP accepts duplicate Host headers
5.3
MEDIUM
CVSS 3.1
EPSS 0.16%
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.
How to fix CVE-2026-34525
To remediate CVE-2026-34525, upgrade the affected package to a fixed version below.
- Debian/python-aiohttp—no fix listed
- —upgrade to 3.13.4 or later
Is CVE-2026-34525 being exploited?
Low — EPSS is 0.2%, meaning exploitation activity has not been observed at scale.
Affected packages (2)
- from 0
- from 0, < 3.13.4
CVSS scores
| Source | Version | Severity | Vector |
|---|---|---|---|
| osv | CVSS 4.0 | — | 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 |
| osv | CVSS 3.1 | MEDIUM5.3 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N |