Medium 6.9Published Jul 30, 2026

CVE-2026-59881AIOHTTP: WebSocket client accepts compressed frames without negotiated permessage-deflate

Updated under an hour ago (Oct 28, 2026, 8:10 AM ET)

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Every CVE for aio-libs aiohttp

Exploited in the last 30 days

AIOHTTP is an asynchronous HTTP client/server framework for asyncio and Python. Prior to 3.14.2, the WebSocket client accepts and decompresses frames with the RSV1 bit set even when the permessage-deflate extension was not negotiated, allowing a malicious server to cause unexpected CPU and memory consumption. This issue is fixed in version 3.14.2.

CVSS: 6.9 MEDIUM (v4.0, CNA)CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N
Weakness (CWE): CWE-20
Known exploited: Not in CISA's KEV catalog
EPSS (exploitation in the next 30 days): Not loaded for this CVE
Assigned by: GitHub_M
NVD analysis: Deferred
Record last updated: Jul 30, 2026
First seen by InfoSec Signals: Oct 9, 2026

Affected products

Affected products

aio-libs aiohttp aio_libs:aiohttp (from the name)	before 3.14.2	CNA record

References

References

https://github.com/aio-libs/aiohttp/security/advisories/GHSA-mq44-7p77-q5h7	x-refsource-confirm
https://github.com/aio-libs/aiohttp/pull/12978	x-refsource-misc
https://github.com/aio-libs/aiohttp/commit/47fb6ae354d4fa22048f4dbe7dbf82b625f0a2f6	x-refsource-misc
http://github.com/aio-libs/aiohttp/releases/tag/v3.14.2	x-refsource-misc

The CVE record on cve.org NVD's entry

The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.