CVE-2026-34525

Updated on 01 Apr 2026

Severity

6.3 Medium severity

Details

CVSS score
6.3
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N

Overview

About vulnerability

Summary

Multiple Host headers were allowed in aiohttp.

Impact

Mostly this doesn’t affect aiohttp security itself, but if a reverse proxy is applying security rules depending on the target Host, it is theoretically possible that the proxy and aiohttp could process different host names, possibly resulting in bypassing a security check on the proxy and getting a request processed by aiohttp in a privileged sub app when using Application.add_domain().


Patch: https://github.com/aio-libs/aiohttp/commit/e00ca3cca92c465c7913c4beb763a72da9ed8349 Patch: https://github.com/aio-libs/aiohttp/commit/53e2e6fc58b89c6185be7820bd2c9f40216b3000

Details

Affected packages:
aiohttp (+2 more)

Fixes