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Fencer Intel
high 7.5

CVE-2026-109527 json

Model Context Protocol Python SDK HTTP and OAuth endpoints allow memory exhaustion through unbounded request bodies

published 26d ago modified 21d ago also EUVD-2026-101514

cvss
7.5
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.7%
EPSS 0.7% chance of exploitation in 30 days, percentile 53%
public exploits
0
none known

Summary

The Model Context Protocol Python SDK is the official Python SDK for Model Context Protocol servers and clients. In mcp versions before 1.29.1 and from 2.0.0a1 through 2.0.1, the Streamable HTTP session manager, SSE message endpoint, and OAuth authorization-server routes buffer complete HTTP request bodies without enforcing a maximum size. An unauthenticated remote client able to reach an affected endpoint can send a large declared or streamed request body that consumes multiple times the body size in process memory and can repeatedly exhaust memory or terminate the server. Stdio-only servers and deployments with an effective upstream request-size limit are not affected, and applications that use StreamableHTTPServerTransport directly remain responsible for enforcing their own limit. The standard SDK server applications and session managers are fixed in versions 1.29.1 and 2.1.0.

Patch / fix

  • lfprojects mcp_python_sdk 1.29.1, 2.1.0
  • python-mcp openSUSE Tumbleweed 1.30.0-1.1

opensuse advisories openSUSE-SU-2026:12475-1

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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-2026-109527 updated cvss 7.5

mcp: mcp: Denial of Service via unbounded HTTP request body buffering

  • Red Hat Ansible Automation Orchestrator 2026 ansible-automation-platform/automation-orchestrator-backend-rhel9 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-service-api-rhel9, openshift-lightspeed/lightspeed-agentic-sandbox-rhel9
    affected: no fix available
  • 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, +1 more
    affected: no fix available, no fix planned “Will not fix”
  • Red Hat Ansible Automation Platform 2 ansible-automation-platform-26/mcp-tools-rhel9, ansible-automation-platform-27/mcp-tools-rhel9, ansible-automation-platform-26/lightspeed-chatbot-rhel9, ansible-automation-platform-27/lightspeed-chatbot-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 Enterprise Linux command line assistant rhel-cla/rhel-knowledge-bridge-rhel10 Red Hat OpenShift AI (RHOAI) rhoai/odh-ogx-core-rhel9, rhoai/odh-feature-server-rhel9, rhoai/odh-llm-d-kv-cache-rhel9, rhoai/odh-llama-stack-core-rhel9, rhoai/odh-th-torch-cuda-py312-rhel9, rhai-early-access/docling-serve-cuda-rhel9, +2 more Red Hat OpenShift Virtualization 4 container-native-virtualization/ocp-virt-validation-checkup-rhel9
    affected: no fix available
  • Red Hat OpenShift AI 3.4 rhoai/odh-kserve-agent-rhel9 1792685313
    fixed: vendor fix RHSA-2026:92510
  • Red Hat Satellite 6.18 satellite/foreman-mcp-server-rhel9 1793272276
    fixed: vendor fix RHSA-2026:92667
  • Red Hat Satellite 6.19 satellite/foreman-mcp-server-rhel9 1793272279
    fixed: vendor fix RHSA-2026:92666
  • Red Hat AI Inference Server rhaiis/vllm-cpu-rhel9, rhaiis/vllm-tpu-rhel9, rhaiis/vllm-cuda-rhel9, rhaiis/vllm-rocm-rhel9
    not affected: vulnerable code not present
  • Red Hat OpenShift AI (RHOAI) rhoai/odh-vllm-gaudi-rhel9, rhoai/odh-kserve-router-rhel9, rhoai/odh-kserve-controller-rhel9, rhoai/odh-openvino-model-server-rhel9
    not affected: component not present
show 1 more
  • Red Hat OpenShift AI 3.4 rhoai/odh-cli-rhel9 1792722177, rhoai/rhai-cli-rhel9 1792722177, rhoai/odh-automl-rhel9 1792697253, rhoai/odh-mlflow-rhel9 1793002327, rhoai/odh-autorag-rhel9 1793265800, rhoai/odh-trainer-rhel9 1792817113, +99 more
    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
yes
Technical impact
partial
Assessed
21d ago

Exploit prediction

0.70% chance of exploitation in the next 30 days, higher than 53% of all scored CVEs (FIRST EPSS, 2026-11-09).

CVSS scores

assigned by version score vector
CNA 3.1 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Affected products

  • modelcontextprotocol python-sdk

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.

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