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TI-2026-20943 Aliases CVE-2026-25905GHSA-pfv4-wmph-5gc6

Lack of isolation in mcp-run-python leads to MCP server takeover

Priority MEDIUM 59CWE-653Published · Updated

Key facts

Attack vector
Network
Privileges required
None
User interaction
Required
Attack complexity
High
Impact type
—
Confidentiality · integrity · availability
Low · Low · Low
Fix status
No fix listed

Attack profile from CVSS 3.1 · CNA. Fix status from CNA and GitHub.

Summary

The Python code being run by 'runPython' or 'runPythonAsync' is not isolated from the rest of the JS code, allowing any Python code to use the Pyodide APIs to modify the JS environment. This may result in an attacker hijacking the MCP server - for malicious purposes including MCP tool shadowing. Note - the "mcp-run-python" project is archived and unlikely to receive a fix.

Why it matters now

Exploitation Proof of concept CISA SSVC · not in CISA KEV
EPSS 0.00204 10th percentileScored 2026-11-07
Fix No fix listed No fixed version in the sources yet

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation
Poc
Automatable
No
Technical impact
Partial

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

Affected products

VendorProductAffected versionsFixed inStatusSource
—mcp-run-pythonall versions—No fix listedCNA
—mcp-run-python (PyPI)up to 0.0.22—No fix listedGHSA-pfv4-wmph-5gc6
  • mcp-run-python Vendor— Affected all versions Fixed in — No fix listed CNA
  • mcp-run-python (PyPI) Vendor— Affected up to 0.0.22 Fixed in — No fix listed GHSA-pfv4-wmph-5gc6

Remediation

No fixed version listed by the sources yet.

Timeline

  1. 2026-10-02 Threatist record created from CVE-2026-25905
  2. 2026-10-03 Alias added: GHSA-pfv4-wmph-5gc6

References

Advisory 2

Other 2

Sources

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