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Fencer Intel
high 8.7

CVE-2026-123817 json

AIOHTTP WebSocket frame reassembly permits excessive memory consumption from tiny reads

published last mo. modified 2d ago also EUVD-2026-120454 , GHSA-2g87-pp6c-29x5

cvss
8.7
version 4.0, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.3%
EPSS 0.3% chance of exploitation in 30 days, percentile 26%
public exploits
0
none known

Summary

AIOHTTP is an asynchronous HTTP client/server framework for asyncio and Python. Prior to 3.14.4, the WebSocket reader retains one bytes object for each transport read while reassembling an incomplete frame. A malicious peer can split a frame into many tiny reads so per-object overhead substantially exceeds the payload bytes allowed by max_msg_size. The condition affects a server receiving frames from a malicious client and a client receiving frames from a malicious server, and can cause excessive memory consumption or denial of service. This issue is fixed in version 3.14.4.

Patch / fix

  • pypi aiohttp 3.14.4

Is CVE-2026-123817 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.

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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-2026-123817 updated cvss 7.5

aiohttp: aiohttp: Denial of Service via memory exhaustion during WebSocket frame reassembly

  • Red Hat Exploit Intelligence exploit-intelligence/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-cpu-rhel9, rhaii/vllm-tpu-rhel9, rhaii/vllm-cuda-rhel9, rhaii/vllm-rocm-rhel9, rhaii/vllm-gaudi-rhel9, rhaii/vllm-spyre-rhel9, +7 more
    affected: workaround, no fix available
  • Red Hat Ansible Automation Platform 2 python-aiohttp 3.9.5-1.el9ap, python3x-aiohttp 3.9.5-1.el8ap, python3.11-aiohttp 3.9.5-1.el9ap, python3.12-aiohttp 3.9.5-4.el8ap, ansible-automation-platform-26/hub-rhel9, ansible-automation-platform-27/hub-rhel9, +17 more
    affected: workaround, no fix available “Fix deferred”
  • 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 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-vllm-cuda-rhel9, rhoai/odh-vllm-rocm-rhel9, rhoai/odh-vllm-gaudi-rhel9, rhoai/odh-ta-lmes-job-rhel9, rhoai/odh-feature-server-rhel9, +22 more Red Hat Satellite 6 python3-aiohttp, python-aiohttp 3.9.5-1.el9ap, python3.12-aiohttp 3.9.5-4.el8ap, satellite/iop-insights-engine-rhel9, satellite/iop-vulnerability-engine-rhel9
    affected: workaround, no fix available
  • Red Hat Ansible Automation Orchestrator 2026 ansible-automation-platform/automation-orchestrator-execution-plane-rhel9 Red Hat OpenShift Lightspeed openshift-lightspeed/lightspeed-agentic-sandbox-rhel9 Red Hat AI Inference Server rhaii-fast/vllm-tpu-rhel9, rhaii-fast/vllm-cuda-rhel9, rhaii-fast/vllm-spyre-rhel9, rhaii-fast/model-opt-cuda-rhel9 Red Hat Ansible Automation Platform 2 automation-controller 4.7.20-1.el9ap, ansible-automation-platform-26/de-minimal-rhel9, ansible-automation-platform-26/ee-minimal-rhel9, ansible-automation-platform-27/de-minimal-rhel9, ansible-automation-platform-27/ee-minimal-rhel9, ansible-automation-platform-26/de-supported-rhel9, +7 more Red Hat Discovery 2 discovery/discovery-server-rhel9 Red Hat OpenShift AI (RHOAI) rhai/guidellm-rhel9, rhoai/odh-mlflow-rhel9, rhoai/odh-autorag-rhel9, rhoai/odh-mlserver-rhel9, rhoai/odh-vllm-cpu-rhel9, rhoai/odh-caikit-nlp-rhel9, +29 more
    +1 more products
    Red Hat Update Infrastructure 4 for Cloud Providers python-aiohttp 3.9.5-1.el9ap
    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

Exploit prediction

0.33% chance of exploitation in the next 30 days, higher than 26% of all scored CVEs (FIRST EPSS, 2026-11-11).

CVSS scores

assigned by version score vector
CNA 4.0 8.7 CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N

Affected packages

ecosystem package affected fixed in
pypi aiohttp
<3.14.4
3.14.4

Affected products

  • aio-libs aiohttp

Classification

Weakness
  • CWE-770 Allocation of Resources Without Limits or Throttling

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.