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Fencer Intel
medium 6.9

CVE-2026-59881 json

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

published 3mo ago modified 19d ago also EUVD-2026-51257 , GHSA-mq44-7p77-q5h7 , PYSEC-2026-3547

cvss
6.9
version 4.0, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.5%
EPSS 0.5% chance of exploitation in 30 days, percentile 44%
public exploits
0
none known

Summary

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.

Patch / fix

  • pypi aiohttp 3.14.2
  • aiohttp aiohttp 3.14.2
  • python-aiohttp Debian 12 3.8.4-1+deb12u2
  • python-aiohttp Debian 14 3.14.3-1

debian advisories DEBIAN-CVE-2026-59881

  • python-aiohttp SLE Module for Public Cloud 15 SP7, SLE Module for Public Cloud 15 SP6, SLE Module for Public Cloud 15 SP5 +1 more 3.6.0-150100.3.41.1
  • python-aiohttp SLE Module for Python 3 15 SP7, SLE Module for Public Cloud 15 SP4 3.9.3-150400.10.46.1
  • python-aiohttp SLES for SAP applications 16.0, SLES 16.0 3.11.16-160000.7.1

suse advisories SUSE-SU-2026:4113-1SUSE-SU-2026:4031-1SUSE-SU-2026:23571-1

  • python-aiohttp openSUSE Leap 16.0 3.11.16-160000.7.1
  • python-aiohttp openSUSE Tumbleweed 3.14.3-1.1

opensuse advisories openSUSE-SU-2026:21687-1openSUSE-SU-2026:11467-1

Is CVE-2026-59881 in your dependencies? Fencer shows which of your repositories are affected as soon as an advisory lands, and opens the fix as a pull request.

Check with Fencer

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2026-59881 updated cvss 5.3

aiohttp: AIOHTTP: Denial of Service via unnegotiated WebSocket compression

  • Red Hat Exploit Intelligence exploit-intelligence-tech-preview/vulnerability-analysis-rhel9 Red Hat Lightspeed Core lightspeed-core/rag-tool-cpu-rhel9, lightspeed-core/lightspeed-stack-rhel9, lightspeed-core/rag-tool-cuda-12.9-rhel9 Red Hat Migration Toolkit for Applications 8 mta/mta-solution-server-rhel9 Red Hat OpenShift Lightspeed openshift-lightspeed/lightspeed-ocp-rag-rhel9, openshift-lightspeed/lightspeed-service-api-rhel9, openshift-lightspeed-tech-preview/lightspeed-rag-tool-rhel9 Red Hat AI Inference Server rhaii/vllm-tpu-rhel9, rhaiis/vllm-cpu-rhel9, rhaiis/vllm-tpu-rhel9, rhaii/vllm-gaudi-rhel9, rhaii/vllm-neuron-rhel9, rhaiis/vllm-spyre-rhel9, +2 more Red Hat Ansible Automation Platform 2 python-aiohttp, automation-controller, ansible-automation-platform-24/hub-rhel8, ansible-automation-platform-25/hub-rhel8, ansible-automation-platform-26/hub-rhel9, ansible-automation-platform-27/hub-rhel9, +32 more
    +9 more products
    Red Hat Ansible Automation Platform Ansible Core 2 ansible-automation-platform/ee-minimal-rhel8, ansible-automation-platform/ee-minimal-rhel9, ansible-automation-platform-tech-preview/ee-minimal-rhel8, ansible-automation-platform-tech-preview/ee-minimal-rhel9 Red Hat Discovery 2 discovery/discovery-server-rhel9 Red Hat Enterprise Linux 9 ansible-core, ansible-test Red Hat Enterprise Linux 10 ansible-core Red Hat Enterprise Linux AI (RHEL AI) 3 rhelai3/bootc-cuda-rhel9, rhelai3/bootc-rocm-rhel9, rhelai3/bootc-gaudi-rhel9, rhelai3/bootc-aws-cuda-rhel9, rhelai3/bootc-gcp-cuda-rhel9, rhelai3/bootc-azure-cuda-rhel9, +1 more Red Hat OpenShift AI (RHOAI) rhoai/odh-automl-rhel9, rhoai/odh-mlflow-rhel9, rhoai/odh-autorag-rhel9, rhoai/odh-mlserver-rhel9, rhoai/odh-caikit-nlp-rhel9, rhoai/odh-vllm-gaudi-rhel9, +46 more Red Hat Satellite 6 python-aiohttp, python3-aiohttp, satellite/iop-insights-engine-rhel9, satellite/iop-vulnerability-engine-rhel9 Red Hat Update Infrastructure 4 for Cloud Providers python-aiohttp Red Hat Update Infrastructure 5 rhui5/rhua-rhel9
    affected: workaround, no fix available “Fix deferred”
  • Red Hat AI Inference Server 3.2 rhaiis/vllm-cuda-rhel9 1790621718, rhaiis/vllm-rocm-rhel9 1790621713, rhaiis/model-opt-cuda-rhel9 1790621714
    fixed: vendor fix RHSA-2026:73859
  • Red Hat AI Inference Server 3.4 rhaii/vllm-cpu-rhel9 1790075793, rhaii/vllm-cuda-rhel9 1790090131, rhaii/vllm-rocm-rhel9 1790109620, rhaii/vllm-spyre-rhel9 1790076141
    fixed: vendor fix RHSA-2026:70965
  • Red Hat Enterprise Linux 9 goose, firefox, glx-utils, mesa-demos, mesa-libGL, firefox-x11, +10 more Red Hat Enterprise Linux 10 goose, firefox, micropipenv, thunderbird Red Hat Hardened Images mariadb11.8 11.8.8-100.hum1
    not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

CISA SSVC

Exploitation
none
Automatable
no
Technical impact
partial
Assessed
3mo ago

Exploit prediction

0.52% chance of exploitation in the next 30 days, higher than 44% of all scored CVEs (FIRST EPSS, 2026-11-11).

CVSS scores

assigned by version score vector
CNA 4.0 6.9 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
CNA 4.0 6.9 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

Affected packages

ecosystem package affected fixed in
pypi aiohttp
<3.14.2
3.14.2

Affected products

  • aio-libs aiohttp

Classification

Weakness
  • CWE-20 Improper Input Validation

References

Sources

Fencer Intel keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.

The maintainers of aio-libs/aiohttp published their own advisory on GitHub. Reviewed sources take precedence over it.

CPEs and fixed versions use Anchore's correction of NVD's data: Added CPE configurations because not yet analyzed by NVD.