CVE-2026-59881

Updated on 30 Jul 2026

Severity

6.9 Medium severity

Details

CVSS score
6.9
CVSS vector
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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

Overview

About vulnerability

Summary

The client accepts and decompresses frames with the RSV1 bit set even when the permessage-deflate extension was not negotiated.

Impact

A client may unexpectedly decompress WebSocket frames when explicitly opted out. This could lead to additional CPU/memory consumption, but is unlikely to be a significant issue unless a zip bomb vulnerability or similar is also present.


Patch: https://github.com/aio-libs/aiohttp/commit/47fb6ae354d4fa22048f4dbe7dbf82b625f0a2f6

Details

Affected packages:
aiohttp @ 3.8.1 (+5 more)

Fixes