CVE-2026-55581 — mcp-shell is an MCP server for running shell commands securely, auditably, and on demand.¶
Key facts
CVE-2026-55581 is a High (8.4) vulnerability: mcp-shell is an MCP server for running shell commands securely, auditably, and on demand.. This entry ships a detection-only PoC and a Docker test lab.
| CVE | CVE-2026-55581 |
| Severity | High (8.4) |
| Detection / prevention | — |
| PoC | poc.py |
| Source | 2026/CVE-2026-55581/ |
Details¶
English | 한국어
Description¶
mcp-shell is an MCP server for running shell commands securely, auditably, and on demand. Prior to 0.6.0, the default Docker security.yaml includes /bin/bash in allowed_executables, while security.go validates only the first token and checkBlockedPatternsAndCommands does not reject the shell command-mode flag -c. A caller of the shell_exec MCP tool can provide the command argument /bin/bash -c <arbitrary-command>, which passes validation and reaches executor.go, where parseCommand and exec.CommandContext execute the arbitrary command as mcpuser outside the intended allowlist. This issue is fixed in version 0.6.0.
Vulnerability Details¶
| Property | Value |
|---|---|
| CVE ID | CVE-2026-55581 |
| Type | RCE |
| CVSS Score | 8.4 |
Proof of Concept¶
Download¶
# Download PoC script
curl -O https://raw.githubusercontent.com/fankh/vulnerability-poc/main/2026/CVE-2026-55581/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-2026-55581
# 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/sonirico/mcp-shell/commit/f31377fce6ec31114e5a4398c0e5270552bce09f
- https://github.com/sonirico/mcp-shell/pull/16
- https://github.com/sonirico/mcp-shell/releases/tag/v0.6.0
- https://github.com/sonirico/mcp-shell/security/advisories/GHSA-3x77-wg38-92r3
- https://github.com/sonirico/mcp-shell/security/advisories/GHSA-3x77-wg38-92r3
Generated by PoC Generator on 2026-08-26T09:40:21.253539579
Frequently asked questions¶
What is CVE-2026-55581?¶
CVE-2026-55581 is a High (8.4) vulnerability: mcp-shell is an MCP server for running shell commands securely, auditably, and on demand.. This entry ships a detection-only PoC and a Docker test lab.
How do I detect CVE-2026-55581?¶
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-2026-55581?¶
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.