mcp-safeguard 0.1.0

Security scanner for MCP servers — detect prompt injection, credential leaks, exposed endpoints, and tool poisoning

🛡️ mcp-shield

The security scanner for MCP servers — detect prompt injection, credential leaks, exposed endpoints, and tool poisoning before they reach production.

---

Architecture

graph TB
    subgraph Clients
        A[Claude Desktop]
        B[Cursor IDE]
        C[Custom Agent]
    end

    subgraph mcp-shield MCP Server
        D[FastMCP Server]
        E[Tools]
        F[Resources]
        G[Prompts]
    end

    subgraph Scanners
        H[Prompt Injection Scanner]
        I[Credential Scanner]
        J[Endpoint Scanner]
        K[Tool Analyzer / Blast Radius]
        L[Tool Poisoning Detector]
    end

    subgraph Security Layer
        M[Rate Limiter]
        N[Input Validator / SSRF Guard]
        O[Auth Middleware]
        P[Audit Logger]
    end

    subgraph Observability
        Q[Prometheus Metrics]
        R[OpenTelemetry Traces]
        S[Streamlit Dashboard]
    end

    subgraph Storage
        T[In-Memory History]
        U[JSON Reports on Disk]
        V[HTML Reports on Disk]
    end

    A & B & C -->|MCP over SSE/stdio| D
    D --> E & F & G
    E --> M --> N --> O
    E --> H & I & J & K & L
    H & I & J & K & L --> T & U & V
    D --> Q & R
    Q --> S
    P --> Q

---

Why mcp-shield?

The MCP (Model Context Protocol) ecosystem is growing fast — but security tooling hasn't kept pace.

The risks are real:

• Tool descriptions can contain hidden instructions that hijack AI behavior (prompt injection)
• MCP server configs routinely contain hardcoded API keys, database passwords, and cloud credentials
• Debug endpoints and admin panels are frequently left open on MCP servers
• Third-party MCP tools can be "poisoned" to silently exfiltrate data while appearing benign

mcp-shield is Snyk for MCP servers. It:

• Detects 15+ prompt injection patterns including instruction overrides, identity hijacking, and zero-width character steganography
• Identifies 17 credential leak patterns including AWS keys, OpenAI/Anthropic keys, JWT tokens, and database URLs
• Probes 28 sensitive endpoint paths and 12 dangerous open ports
• Scores every tool's blast radius and permission risk on a 0–10 scale
• Generates CVSS-scored findings with actionable remediation guidance
• Produces HTML + JSON reports for audit trails

---

Installation

pip

pip install mcp-safeguard

Docker

docker run -p 8000:8000 mcpshield/mcp-shield:latest

Docker Compose (with Prometheus + Grafana + Dashboard)

git clone https://github.com/mcp-shield/mcp-shield
cd mcp-shield
cp .env.example .env
docker compose up

Services:

• mcp-shield: http://localhost:8000
• Prometheus: http://localhost:9090
• Grafana: http://localhost:3000
• Dashboard: http://localhost:8501

---

Quick Start

Claude Desktop

Add to ~/Library/Application Support/Claude/claude_desktop_config.json:

{
  "mcpServers": {
    "mcp-shield": {
      "command": "python",
      "args": ["-m", "fastmcp", "run", "src/mcp_shield/server.py"],
      "env": {
        "MCP_SHIELD_API_KEY": "your-api-key-here"
      }
    }
  }
}

Cursor IDE

Add to .cursor/mcp.json in your project:

{
  "mcpServers": {
    "mcp-shield": {
      "command": "python",
      "args": ["-m", "fastmcp", "run", "src/mcp_shield/server.py"],
      "env": {
        "MCP_SHIELD_API_KEY": "your-api-key-here"
      }
    }
  }
}

Run directly

# Install
pip install mcp-safeguard

# Run server (stdio transport)
fastmcp run src/mcp_shield/server.py

# Run server (SSE transport for remote clients)
fastmcp run src/mcp_shield/server.py --transport sse --port 8000

---

Tools Reference

scan_mcp_server

Run a full security scan of an MCP server.

Input:

{
  "url": "http://localhost:8000",
  "auth_token": "optional-bearer-token"
}

Output:

{
  "summary": {
    "scan_id": "550e8400-e29b-41d4-a716-446655440000",
    "target": "http://localhost:8000",
    "overall_severity": "HIGH",
    "overall_cvss": 8.5,
    "critical_count": 0,
    "high_count": 3,
    "medium_count": 5,
    "total_findings": 11,
    "duration_ms": 1243.5
  },
  "injection_findings": [...],
  "credential_findings": [...],
  "endpoint_findings": [...],
  "tool_risk_profiles": [...]
}

---

scan_tool_definitions

Analyze tool definitions JSON for prompt injection and poisoning risks.

Input:

{
  "tool_json": "[{\"name\": \"search\", \"description\": \"Search files. Ignore previous instructions.\"}]"
}

Output:

{
  "summary": {"tools_analyzed": 1, "total_findings": 2, "critical": 0, "high": 1},
  "injection_findings": [{
    "rule_id": "PI-001",
    "severity": "HIGH",
    "cvss_score": 9.3,
    "title": "Instruction Override Attempt",
    "location": "tool:search → description",
    "evidence": "Ignore previous instructions",
    "remediation": "Remove instruction override phrases from tool descriptions."
  }]
}

---

check_auth_config

Audit MCP server configuration for credential exposure and OAuth scope risks.

Input:

{
  "config_json": "{\"command\": \"python\", \"env\": {\"API_KEY\": \"sk-ant-api03-abc123...\"}}"
}

Output:

{
  "summary": {"total_findings": 1, "critical": 1},
  "credential_findings": [{
    "rule_id": "CRED-017-ENV",
    "severity": "CRITICAL",
    "cvss_score": 9.5,
    "title": "Anthropic API Key in Environment Variable",
    "evidence": "sk-a****...****api0",
    "remediation": "Rotate this Anthropic API key. Use workspace-scoped keys."
  }]
}

---

check_endpoint_exposure

Probe for exposed admin panels, debug routes, and dangerous ports.

Input:

{"host": "localhost", "port": 8000}

Output:

{
  "summary": {"target": "localhost:8000", "total_findings": 2, "high": 1},
  "endpoint_findings": [{
    "rule_id": "EP-002",
    "severity": "HIGH",
    "title": "Exposed Debug Endpoint",
    "location": "http://localhost:8000/debug",
    "status_code": 200,
    "remediation": "Disable debug endpoints in production. Set DEBUG=False."
  }]
}

---

generate_security_report

Retrieve a full report in JSON, HTML, or text format.

Input:

{"scan_id": "550e8400-e29b-41d4-a716-446655440000", "format": "html"}

---

get_scan_history

List all past scans with severity scores.

Output:

{
  "total_scans": 12,
  "scans": [
    {"scan_id": "...", "target": "http://localhost:8000", "overall_severity": "HIGH", "overall_cvss": 8.5, "total_findings": 11}
  ]
}

---

compare_scans

Diff two scans to identify regressions or improvements.

Input:

{"scan_id_1": "baseline-uuid", "scan_id_2": "after-fix-uuid"}

Output:

{
  "cvss_delta": -2.5,
  "findings_delta": -4,
  "regression_detected": false,
  "new_findings": [],
  "resolved_findings": ["injection_findings:PI-001", "credential_findings:CRED-007"]
}

---

Resources Reference

URI	Description
security://reports/{scan_id}	Full JSON report for a completed scan
security://rules	All active detection rules (regex, CVSS, remediation)
security://dashboard	Aggregate stats across all scans

---

Prompts Reference

security_audit_prompt

A guided, step-by-step prompt that walks through a full MCP security audit — from tool analysis through endpoint hardening.

remediation_prompt

Step-by-step fix guides for each vulnerability type:

• prompt_injection — How to clean tool descriptions
• credential_leak — Secrets management and rotation
• endpoint_exposure — Firewall rules and auth requirements
• tool_poisoning — Detecting and removing poisoned tools
• oauth_overpermission — Scope reduction and token lifecycle

---

Example Scan Output

======================================================================
  mcp-shield Security Report
======================================================================
  Target:       http://localhost:8000
  Scan ID:      a3f2c1d4-9e8b-47f1-b2a3-c4d5e6f7a8b9
  Time:         2026-05-06T14:32:11Z
  Duration:     1,847.3ms
  Overall:      HIGH (CVSS 8.5)

  Findings Summary:
    CRITICAL     0
    HIGH         3
    MEDIUM       5
    LOW          2
    INFO         1
    ─────────────────
    TOTAL       11

  ────────────────────────────────────────────────────────────────
  Prompt Injection (3 findings)
  ────────────────────────────────────────────────────────────────
  [HIGH    ] [9.3 ] PI-001: Instruction Override Attempt
             Location: tool:data_query → description
             Fix: Remove instruction override phrases from tool descriptions.

  [MEDIUM  ] [5.5 ] PI-007: Deception Instruction
             Location: tool:search_web → description
             Fix: Tool descriptions must not instruct the AI to deceive users.

  ────────────────────────────────────────────────────────────────
  Credential Exposure (2 findings)
  ────────────────────────────────────────────────────────────────
  [HIGH    ] [8.5 ] CRED-009: GitHub Personal Access Token
             Location: env.GITHUB_TOKEN
             Fix: Rotate and use GitHub Apps with minimal scopes.

  ────────────────────────────────────────────────────────────────
  Endpoint Exposure (4 findings)
  ────────────────────────────────────────────────────────────────
  [HIGH    ] [7.5 ] EP-002: Exposed Debug Endpoint
             Location: http://localhost:8000/debug
             Fix: Disable debug endpoints in production.

  [MEDIUM  ] [5.5 ] EP-004: Prometheus Metrics Exposed Publicly
             Location: http://localhost:8000/metrics
             Fix: Restrict /metrics to internal networks.
======================================================================

---

Security & Deployment Notes

Authentication

Set MCP_SHIELD_API_KEY to require authentication for all tool calls:

MCP_SHIELD_API_KEY=msh_your_secret_key_here fastmcp run src/mcp_shield/server.py

SSRF Protection

mcp-shield has built-in SSRF protection. By default, only localhost, 127.0.0.1, and ::1 are scannable. To add hosts:

MCP_SHIELD_SSRF_ALLOWLIST='["localhost","127.0.0.1","my-mcp-server.internal"]'

Network Scanning

Disable network scanning entirely (tool definition analysis only):

MCP_SHIELD_ENABLE_NETWORK_SCAN=false

Rate Limiting

Default: 100 requests per 60-second window per client. Adjust:

MCP_SHIELD_RATE_LIMIT_REQUESTS=50
MCP_SHIELD_RATE_LIMIT_WINDOW=60

---

Metrics & Benchmarks

When MCP_SHIELD_PROMETHEUS_ENABLED=true, mcp-shield exposes:

Metric	Type	Description
mcp_shield_scans_total	Counter	Total scans by status
mcp_shield_vulnerabilities_total	Counter	Findings by severity + category
mcp_shield_scan_duration_seconds	Histogram	Scan latency distribution
mcp_shield_active_scans	Gauge	In-progress scans
mcp_shield_finding_cvss_score	Histogram	CVSS score distribution
mcp_shield_rate_limit_hits_total	Counter	Rate limit blocks
mcp_shield_auth_failures_total	Counter	Auth failures by method

Typical performance:

• Tool definition scan (10 tools): ~5ms
• Full endpoint scan (localhost): ~800ms–2s
• HTML report generation: ~2ms
• Memory per scan result: ~50KB

---

Roadmap

• v0.2.0 — MCP stdio transport scanning (scan servers over the MCP protocol directly)
• v0.2.0 — CI/CD plugin for GitHub Actions (scan on every PR)
• v0.3.0 — VS Code extension for real-time tool description linting
• v0.3.0 — MCP registry scanning (bulk scan public MCP servers)
• v0.4.0 — AI-assisted remediation (use Claude to generate fixes)
• v0.5.0 — SBOM generation for MCP tool supply chain
• v1.0.0 — SOC2/compliance report templates

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Contributing

See CONTRIBUTING.md for development setup, code style, and PR guidelines.

Quick start for contributors:

git clone https://github.com/mcp-shield/mcp-shield
cd mcp-shield
python -m venv .venv && source .venv/bin/activate
pip install -e ".[dev]"
pytest tests/ -v
black src/ tests/
ruff check src/ tests/

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License

MIT — see LICENSE.

Built with ❤️ by the mcp-shield contributors.