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

Quick assessment

Affected
aio-libs aiohttp
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

aio-libs aiohttp是aio-libs的异步HTTP客户端/服务器框架。 aio-libs Async http client/server framework 3.14.2之前版本存在输入验证错误漏洞，该漏洞源于WebSocket客户端接受并解压设置了RSV1位的帧，即使没有协商permessage-deflate扩展，导致意外的CPU和内存消耗。

CVSS 6.9 · Medium EPSS 0.52% · P42

Affected Version Matrix 1

VendorProduct Version RangeStatus
aio-libs aiohttp < 3.14.2 affected
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I. Basic Information for CVE-2026-59881

Vulnerability Information
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Vulnerability Title
AIOHTTP: WebSocket client accepts compressed frames without negotiated permessage-deflate
Source: CVE Program / CVE List V5
Vulnerability 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.
Source: CVE Program / CVE List V5
CVSS Information
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
Source: CVE Program / CVE List V5
Vulnerability Type
输入验证不恰当
Source: CVE Program / CVE List V5
Vulnerability Title
aio-libs Async http client/server framework 输入验证错误漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
aio-libs aiohttp是aio-libs的异步HTTP客户端/服务器框架。 aio-libs Async http client/server framework 3.14.2之前版本存在输入验证错误漏洞，该漏洞源于WebSocket客户端接受并解压设置了RSV1位的帧，即使没有协商permessage-deflate扩展，导致意外的CPU和内存消耗。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
aio-libs aiohttp < 3.14.2 -

II. Public POCs for CVE-2026-59881

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III. Intelligence Information for CVE-2026-59881

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Patches & Fixes for CVE-2026-59881 (3)

Vendor Advisories for CVE-2026-59881 (1)

IV. Related Vulnerabilities

Same product: aiohttp
Same vendor: aio-libs
Same weakness: CWE-20

V. Comments for CVE-2026-59881

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