---
id: CVE-2026-81096
title: >-
  ToolUniverse ran caller-supplied Python inside a sandbox that could be
  escaped, on a server that required no authentication
summary: >-
  ToolUniverse ran caller-supplied Python inside a sandbox that could be
  escaped, on a server that required no authentication. The executor behind the
  python_code_executor tool, in python_executor_tool.py, inspected the submitted
  source fo…
severity: critical
cvss: 10
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H'
cwe:
  - CWE-94
published: '2026-08-27'
updated: '2026-09-23'
sourceUpdated: '2026-09-23T17:17:42.553'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-81096'
references:
  - url: 'https://github.com/mims-harvard/ToolUniverse'
    label: disclosure@vulncheck.com
  - url: 'https://github.com/mims-harvard/ToolUniverse/pull/251'
    label: disclosure@vulncheck.com
  - url: >-
      https://github.com/mims-harvard/ToolUniverse/security/advisories/GHSA-pxwq-22vf-87fm
    label: disclosure@vulncheck.com
  - url: >-
      https://www.vulncheck.com/advisories/tooluniverse-through-1.2.6-unauthenticated-remote-code-execution-via-python-code-executor-sandbox-escape
    label: disclosure@vulncheck.com
tags:
  - nvd
epss: 0.00574
epssPercentile: 0.46142
ingestedAt: '2026-09-23T17:28:14.806Z'
---

## Overview

ToolUniverse ran caller-supplied Python inside a sandbox that could be escaped, on a server that required no authentication. The executor behind the python_code_executor tool, in python_executor_tool.py, inspected the submitted source for a denied list of attribute names and calls but left the attribute-lookup builtins available and did not stop a dunder attribute reached through a string lookup or through a module already permitted, so a caller could walk from a literal's class to its base and enumerate subclasses to obtain a reference to the process and subprocess modules. A per-call argument also let the caller widen the import allow-list before the inspection ran. The HTTP and MCP servers in http_api_server.py and smcp_server.py bound to every interface with debugging enabled and no authentication, so any caller able to reach the port executed code as the server process. Version 1.3.0 adds bearer-token authentication, defaults the bind address to loopback, and hardens the attribute checks.

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.