How severe is CVE-2026-25905?

CVE-2026-25905 has a CVSS 3.x base score of 5.8, rated medium severity. It is exploitable over network with high attack complexity, requires no privileges and user interaction. Impact on confidentiality is low, integrity low, and availability low.

Is CVE-2026-25905 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (7th percentile), an estimate of the probability of exploitation in the next 30 days.

How do I fix CVE-2026-25905?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.

Does CVE-2026-25905 have an EU (EUVD) identifier?

Yes. CVE-2026-25905 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-6610.

When was CVE-2026-25905 published?

CVE-2026-25905 was published on 2026-02-09 and last updated on 2026-06-17.

CVE-2026-25905

CVE-2026-25905 is a medium-severity vulnerability with a CVSS 3.x base score of 5.8. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-653.

Key facts

Severity: Medium (CVSS 3.x base score 5.8)
EPSS exploit prediction: 0% (7th percentile)
Actively exploited: Not listed in CISA KEV
EU (EUVD) id: EUVD-2026-6610
Weakness: CWE-653
Published: 2026-02-09
Last modified: 2026-06-17

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.

Frequently asked questions

What is CVE-2026-25905?: 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.
How severe is CVE-2026-25905?: CVE-2026-25905 has a CVSS 3.x base score of 5.8, rated medium severity. It is exploitable over network with high attack complexity, requires no privileges and user interaction. Impact on confidentiality is low, integrity low, and availability low.
Is CVE-2026-25905 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (7th percentile), an estimate of the probability of exploitation in the next 30 days.
How do I fix CVE-2026-25905?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
Does CVE-2026-25905 have an EU (EUVD) identifier?: Yes. CVE-2026-25905 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-6610.
When was CVE-2026-25905 published?: CVE-2026-25905 was published on 2026-02-09 and last updated on 2026-06-17.

References

https://research.jfrog.com/vulnerabilities/mcp-run-python-lack-of-isolation-mcp-takeover-jfsa-2026-001653030/

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