Vulnerability · Published Feb 9, 2026 · Assigned by JFROG
CVE-2026-25905Lack of isolation in mcp-run-python leads to MCP server takeover
Medium 5.8
In plain English
A medium-severity security flaw in mcp-run-python. Proof-of-concept exploit code is public. The chance it is exploited in the next 30 days is estimated at 0.2% (higher than 10% of all known vulnerabilities).
Severity (CVSS 3.1)5.8Medium
Exploit odds (30 days)0.2%top 89.6% of all CVEs
Exploited in the wildNo reportsCISA SSVC: poc
Attack toolingNoneno public tooling known
Official description
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.
Affected packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| PyPI | mcp-run-python | no fix listed | GHSA-pfv4-wmph-5gc6 |
| PyPI | mcp-run-python | no fix listed | PYSEC-2026-2628 |
Affected products (as reported)
| Vendor | Product | Versions |
|---|---|---|
| mcp-run-python | 0 |
Weakness: CWE-653 · Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:C/C:L/I:L/A:L