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TI-2025-40852 Aliases CVE-2025-66416GHSA-9h52-p55h-vw2f

DNS Rebinding Protection Disabled by Default in Model Context Protocol Python SDK for Servers Running on Localhost

Priority LOW 36CWE-1188Published · Updated

Key facts

Attack vector
Network
Privileges required
None
User interaction
Passive
Attack complexity
Low
Attack requirements
Present
Impact type
—
Confidentiality · integrity · availability
High · High · None
Fix status
Partial Red Hat: 4 fixed, 2 without a fix

Attack profile from CVSS 4.0 · CNA. Fix status from CNA, GitHub and Red Hat.

Summary

The MCP Python SDK, called `mcp` on PyPI, is a Python implementation of the Model Context Protocol (MCP). Prior to version 1.23.0, tThe Model Context Protocol (MCP) Python SDK does not enable DNS rebinding protection by default for HTTP-based servers. When an HTTP-based MCP server is run on localhost without authentication using FastMCP with streamable HTTP or SSE transport, and has not configured TransportSecuritySettings, a malicious website could exploit DNS rebinding to bypass same-origin policy restrictions and send requests to the local MCP server. This could allow an attacker to invoke tools or access resources exposed by the MCP server on behalf of the user in those limited circumstances. Note that running HTTP-based MCP servers locally without authentication is not recommended per MCP security best practices. This issue does not affect servers using stdio transport. This vulnerability is fixed in 1.23.0.

Why it matters now

Exploitation None reported CISA SSVC · not in CISA KEV
EPSS 0.00544 45th percentileScored 2026-11-07
Fix Partial python-sdk (modelcontextprotocol): 1.23.0mcp (PyPI): 1.23.0Red Hat: 4 advisoriesRed Hat: 4 fixed, 2 without a fix

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation
None
Automatable
No
Technical impact
Total

The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.

Affected products

VendorProductAffected versionsFixed inStatusSource
MLflowpython-sdkbefore 1.23.01.23.0Patch availableCNA
—mcp (PyPI)before 1.23.01.23.0Patch availableGHSA-9h52-p55h-vw2f
  • python-sdk VendorMLflow Affected before 1.23.0 Fixed in 1.23.0 Patch available CNA
  • mcp (PyPI) Vendor— Affected before 1.23.0 Fixed in 1.23.0 Patch available GHSA-9h52-p55h-vw2f

CPE configurations NVD · 1

CPEVersionsRoleVendor
cpe:2.3:a:lfprojects:mcp_python_sdk:*:*:*:*:*:*:*:*before 1.23.0VulnerableMLflow
  • cpe:2.3:a:lfprojects:mcp_python_sdk:*:*:*:*:*:*:*:* Versions before 1.23.0 Vulnerable ·MLflow

Remediation

  • Fix · CNA python-sdk (modelcontextprotocol) Fixed in 1.23.0
  • Fix · GHSA-9h52-p55h-vw2f mcp (PyPI) Fixed in 1.23.0 Advisory →

Red Hat 4 advisories

  • RHSA-2026:3713 Released 2026-03-04 · Red Hat rating Critical
    RHOAI 3.3 - Red Hat OpenShift AI
    • Red Hat OpenShift AI 3.3 registry.redhat.io/rhoai/odh-built-in-detector-rhel9, registry.redhat.io/rhoai/odh-dashboard-rhel9, registry.redhat.io/rhoai/odh-data-science-pipelines-argo-argoexec-rhel9 +47
  • RHSA-2026:1596 Released 2026-01-29 · Red Hat rating Important
    Red Hat Ansible Automation Platform 2.6 Container Release Update
    • Red Hat Ansible Automation Platform 2.6 registry.redhat.io/ansible-automation-platform-26/controller-rhel9, registry.redhat.io/ansible-automation-platform-26/controller-rhel9-operator, registry.redhat.io/ansible-automation-platform-26/de-minimal-rhel9 +7
  • RHSA-2026:0629 Released 2026-01-14 · Red Hat rating Important
    satellite/foreman-mcp-server-rhel9 container image available as a Technology Preview
    • Red Hat Satellite 6.18 registry.redhat.io/satellite/foreman-mcp-server-rhel9
Show 1 more Red Hat advisories
  • RHSA-2025:23531 Released 2025-12-17 · Red Hat rating Important
    RHOAI 2.25.1 - Red Hat OpenShift AI
    • Red Hat OpenShift AI 2.25 registry.redhat.io/rhoai/odh-built-in-detector-rhel9, registry.redhat.io/rhoai/odh-caikit-nlp-rhel9, registry.redhat.io/rhoai/odh-caikit-tgis-serving-rhel9 +34

Vendor assessments

Red Hat

Red Hat rating: Important. Red Hat's page for this CVE →

ProductStatusPlan or fix
OpenShift LightspeedAffectedNo fix yet
Red Hat OpenShift AI (RHOAI)AffectedNo fix yet
Red Hat Ansible Automation Platform 2.6Fixed RHSA-2026:1596
Red Hat OpenShift AI 2.25Fixed RHSA-2025:23531
Red Hat OpenShift AI 3.3Fixed RHSA-2026:3713
Red Hat Satellite 6.18Fixed RHSA-2026:0629
Not affected: 4 products
  • Red Hat Ansible Automation Platform 2
  • Red Hat Ansible Automation Platform 2.6
  • Red Hat OpenShift AI 2.25
  • Red Hat OpenShift AI 3.3

Timeline

  1. 2026-10-02 Threatist record created from CVE-2025-66416
  2. 2026-10-03 Alias added: GHSA-9h52-p55h-vw2f

References

Patch 1

Advisory 3

Other 3

  • TI-2026-42756 MCP Python SDK: WebSocket server transport does not support Host/Origin validation CVSS 4.0HIGH 7.6
  • TI-2026-37970 MCP Python SDK: HTTP transports serve session requests without verifying the authenticated principal CVSS 3.1HIGH 7.1
  • TI-2026-37971 MCP Python SDK: Experimental task handlers allow any client to access and cancel other clients' tasks CVSS 3.1HIGH 7.6

Sources

This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences