WebSocket Client Vulnerability in AIOHTTP Framework by aio-libs
CVE-2026-59881

6.9MEDIUM

Key Information:

Vendor

Aio-libs

Status
Aiohttp
Vendor
CVE Published:
30 July 2026

What is CVE-2026-59881?

The AIOHTTP framework, an asynchronous HTTP client/server for Python, has a vulnerability in its WebSocket client. Prior to version 3.14.2, the WebSocket client was susceptible to accepting and decompressing frames with the RSV1 bit set, even without the negotiation of the permessage-deflate extension. This flaw could be exploited by a malicious server, potentially leading to excessive CPU and memory usage. This issue has been rectified in version 3.14.2.

Affected Version(s)

aiohttp < 3.14.2

References

https://github.com/aio-libs/aiohttp/security/advisories/G...
x_refsource_CONFIRM
https://github.com/aio-libs/aiohttp/pull/12978
x_refsource_MISC
https://github.com/aio-libs/aiohttp/commit/47fb6ae354d4fa...
x_refsource_MISC

CVSS V4

Score:
6.9
Severity:
MEDIUM
Confidentiality:
None
Integrity:
None
Availability:
Low
Attack Vector:
Network
Attack Complexity:
Low
Attack Required:
None
Privileges Required:
Undefined
User Interaction:
None

Timeline

  • Vulnerability published

  • Vulnerability Reserved

.