Medium severity · published Jul 30, 2026
CVE-2026-59881
AIOHTTP: WebSocket client accepts compressed frames without negotiated permessage-deflate
6.9
CVSS
0.5%
EPSS
No
On KEV
Description
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.
Exploitation
Is it being used?
Exploit prediction (EPSS)0.5% · higher than 44% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
AI
aiohttp · aio-libs
< 3.14.2 · source: vendor
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-59881
CVE.org
https://www.cve.org/CVERecord?id=CVE-2026-59881
github.com
http://github.com/aio-libs/aiohttp/releases/tag/v3.14.2
github.com
https://github.com/aio-libs/aiohttp/commit/47fb6ae354d4fa22048f4dbe7dbf82b625f0a2f6
github.com
https://github.com/aio-libs/aiohttp/pull/12978
github.com
https://github.com/aio-libs/aiohttp/security/advisories/GHSA-mq44-7p77-q5h7
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