CVE-2026-34525mediumCWE-20 CWE-444

AIOHTTP: Duplicate Host header accepted

13Vexday Risk Score

No sign of exploitation. No public exploitation artifact known so far.

ssvc Trackcvss 6.3epss 0.3%

exploitation probability

0.3%top 79% of all CVEs

observed exploitation

nono source reports it

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: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 products

aio-libs · aiohttp

References

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 https://github.com/aio-libs/aiohttp/security/advisories/GHSA-c427-h43c-vf67