CVE-2026-25905Public exploitNetwork attack vector

MCP server takeover via exposed JavaScript bridge

Published Feb 9, 2026 · Updated Feb 9, 2026

Improper isolation in Pydantic mcp-run-python 0.0.22 and earlier allows remote attackers to take over the MCP server via submitted Python code. The runPython and runPythonAsync functions expose Pyodide's JavaScript bridge to untrusted code, which can overwrite shared runtime objects. The server must execute attacker-influenced code, directly or through an AI model; exploitation can shadow MCP tools and alter later server behavior.

CVSS severity5.8
Medium
EPSS probability0.18%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Improper isolation in Pydantic mcp-run-python 0.0.22 and earlier allows remote attackers to take over the MCP server via submitted Python code. The runPython and runPythonAsync functions expose Pyodide's JavaScript bridge to untrusted code, which can overwrite shared runtime objects. The server must execute attacker-influenced code, directly or through an AI model; exploitation can shadow MCP tools and alter later server behavior.

The record

CVE
CVE-2026-25905
Published
Feb 9, 2026
Updated
Feb 9, 2026
Vendor
Pydantic
Product
mcp-run-python
Classifications
CWE-653, T1059.006
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Feb 9, 2026CVE publishedPublication date reported by the CVE source.
  2. Feb 9, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=0

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Pydantic · mcp-run-pythonversion=0

Published CVSS scores

5.8GitHub Advisory DatabaseCVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:C/C:L/I:L/A:L

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-653Improper Isolation or Compartmentalization
T1059.006Command and Scripting Interpreter: Python

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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