MCP Run Python Deno Sandbox Misconfiguration Allows SSRF Attacks via Localhost Access

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

5.8 · CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:C/C:L/I:L/A:L

EPSS

• CVE-2026-25904: 0.19% estimated exploitation activity in the next 30 days; percentile 8.91 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Impact Server-Side Request Forgery (SSRF): A security vulnerability exists in the mcp-run-python tool (specifically within the Pydantic-AI integration) due to an overly permissive Deno sandbox configuration. The tool configures the Deno runtime—which is intended to isolate the execution of untrusted Python code—with network permissions that include access to the host's loopback interface (localhost). Consequently, malicious Python code executed through the tool can bypass network isolation and send HTTP requests to internal services running on the host machine. This allows attackers to interact with local APIs, databases, or cloud metadata services that should not be accessible from the sandbox. Patches No Patch Available: The mcp-run-python project is currently archived and maintainers have indicated it is unlikely to receive a fix. Recommendation: Users are strongly advised to immediately stop using this package. If functionality is required, users must migrate to an alternative…

Published by the source

9 Feb 2026, 09:30 UTC

Last modified by the source

13 Jul 2026, 16:43 UTC

Source last checked

26 Oct 2026, 13:36 UTC

1. Revision 2 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-6fgp-m6q4-j3q5

2. Revision 1 · created · 24 Oct 2026

   Published from osv record GHSA-6fgp-m6q4-j3q5

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# Patch Next advisory brief: CVE-2026-25904

Advisory: MCP Run Python Deno Sandbox Misconfiguration Allows SSRF Attacks via Localhost Access
IDs: CVE-2026-25904, GHSA-6fgp-m6q4-j3q5
Record: https://patchnext.com/advisories/cve-2026-25904 (revision 2, source checked 26 Oct 2026, 13:36 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 5.8)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor response not established. A vendor fix does not mean a deployment is fixed.

## Affected components
- PyPI mcp-run-python: affected <= 0.0.22

## Suggested inspection (read-only)
- `python -m pip show mcp-run-python`: prints the installed version. Run with the environment that serves production active.

## Supported action
No complete vendor fix is recorded. Follow the primary source's mitigation guidance and check this record again before closing anything.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on mcp-run-python.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://osv.dev/vulnerability/GHSA-6fgp-m6q4-j3q5 (OSV record GHSA-6fgp-m6q4-j3q5 lists affected ranges: PyPI mcp-run-python >=0 <=0.0.22)
- Verified: https://github.com/advisories/GHSA-6fgp-m6q4-j3q5 (GitHub-reviewed advisory GHSA-6fgp-m6q4-j3q5 lists affected ranges: PyPI mcp-run-python >=0 <=0.0.22)

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