CVE-2026-81096 — ToolUniverse ran caller-supplied Python inside a sandbox that could be escaped, on a…¶

Key facts

CVE-2026-81096 is a Critical (10.0) vulnerability: ToolUniverse ran caller-supplied Python inside a sandbox that could be escaped, on a…. This entry ships a detection-only PoC and a Docker test lab.


CVE	CVE-2026-81096
Severity	Critical (10.0)
Detection / prevention	—
PoC	poc.py
Source	2026/CVE-2026-81096/

Details¶

English | 한국어

Description¶

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.

Vulnerability Details¶

Property	Value
CVE ID	CVE-2026-81096
Type	RCE
CVSS Score	10.0

Proof of Concept¶

Download¶

# Download PoC script
curl -O https://raw.githubusercontent.com/fankh/vulnerability-poc/main/2026/CVE-2026-81096/poc.py

Usage¶

# Run PoC against target
python3 poc.py --target <TARGET_URL>

# With authentication
python3 poc.py --target <TARGET_URL> --username <USER> --password <PASS>

⚠️ Warning: This PoC is for authorized security testing only. It uses detection-only techniques and does not exploit or damage target systems.

Test Lab¶

This repository includes a Docker-based test environment with both vulnerable and patched applications.

Quick Start¶

# Clone and navigate to CVE directory
cd CVE-2026-81096

# Start both applications
docker-compose up -d

# Run tests
./run-tests.sh    # Linux/Mac
./run-tests.ps1   # Windows PowerShell

Application Endpoints¶

Application	URL	Status
Vulnerable App	http://localhost:8080	Shows vulnerability
Patched App	http://localhost:8081	Demonstrates fix

Directory Structure¶

├── README.md           # English documentation
├── README_KO.md        # Korean documentation
├── poc.py              # PoC detection script
├── docker-compose.yml  # Container orchestration
├── run-tests.sh        # Linux/Mac test runner
├── run-tests.ps1       # Windows test runner
├── vulnerable-app/     # Vulnerable version
│   ├── app.py
│   ├── Dockerfile
│   └── requirements.txt
└── patched-app/        # Fixed version
    ├── app.py
    ├── Dockerfile
    └── requirements.txt

References¶

https://github.com/mims-harvard/ToolUniverse
https://github.com/mims-harvard/ToolUniverse/pull/251
https://github.com/mims-harvard/ToolUniverse/security/advisories/GHSA-pxwq-22vf-87fm
https://www.vulncheck.com/advisories/tooluniverse-through-1.2.6-unauthenticated-remote-code-execution-via-python-code-executor-sandbox-escape

Generated by PoC Generator on 2026-08-30T12:07:25.523537895

Frequently asked questions¶

What is CVE-2026-81096?¶

CVE-2026-81096 is a Critical (10.0) vulnerability: ToolUniverse ran caller-supplied Python inside a sandbox that could be escaped, on a…. This entry ships a detection-only PoC and a Docker test lab.

How do I detect CVE-2026-81096?¶

Run the detection-only PoC included with this entry against your Docker test lab to confirm whether a target is affected; pair it with your own IDS logging.

How do I block or mitigate CVE-2026-81096?¶

Upgrade to a fixed version per the vendor advisory; the NVD record lists the affected versions. Use the included PoC to verify your remediation.

For authorized security testing and research only. See the full source and NVD record.