MCP Security Audit

Executive Summary

Overall Risk: CRITICAL

Security Score: 0/100

Production Readiness: 🔴 NOT READY

The reviewed MCP server exposes several high-impact capabilities without visible authorization boundaries or sufficient restrictions. The most serious issue is arbitrary operating-system command execution through run_command(command), which can provide complete control of the server with the privileges of the production service account.

Additional risks include unrestricted filesystem access, unrestricted outbound URL fetching, and insufficient evidence of per-user authorization for customer data.

Immediate remediation is recommended before production deployment.

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Attack-Surface Summary

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Critical Findings

[MCP-001] Arbitrary Command Execution

• Severity: CRITICAL
• Confidence: CONFIRMED
• Category: Command execution
• Affected component: run_command
• Evidence: The tool accepts a caller-controlled command and executes it on the host.
• Risk: A caller may execute arbitrary operating-system commands with the privileges available to the MCP server.
• Attack path: MCP client → run_command → shell/OS → server resources.

Recommended fix: Remove arbitrary shell execution. Replace it with narrowly scoped, allowlisted operations that expose only the required functionality.

Verification: In an isolated test environment, attempt representative disallowed commands and confirm that arbitrary execution is impossible.

• Priority: Immediate

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High Findings

[MCP-002] Unrestricted Filesystem Access

• Severity: HIGH
• Confidence: CONFIRMED
• Category: Filesystem security
• Affected component: read_file
• Evidence: The tool accepts a filesystem path without a demonstrated allowlist or sandbox.

Risk: Sensitive application files, configuration files, credentials, or other host data could potentially be disclosed.

Recommended fix: Restrict access to an application-owned directory, canonicalize paths, reject traversal, and apply filesystem permissions or sandboxing.

Verification: Test normal paths, absolute paths, parent-directory traversal, encoded traversal, and symlink cases.

[MCP-003] Unrestricted Outbound URL Fetching

• Severity: HIGH
• Confidence: CONFIRMED
• Category: SSRF/network security
• Affected component: fetch_url
• Evidence: Arbitrary URLs are accepted from the caller.

Risk: The server may be abused to access internal services or other network destinations that should not be reachable.

Recommended fix: Apply destination allowlists, safe URL parsing, redirect restrictions, network egress controls, and appropriate timeouts.

• Verification: In a controlled environment, verify that unauthorized private/internal destinations are rejected.

[MCP-004] Missing Demonstrated Per-User Authorization

• Severity: HIGH
• Confidence: LIKELY
• Category: Authorization
• Affected component: get_customer
• Evidence: The supplied description states that per-tool authorization checks are not visible.
• Risk: One caller may potentially retrieve customer information belonging to another user or tenant.

Recommended fix: Enforce authorization server-side for every customer-data operation and derive identity from a trusted authentication mechanism rather than caller-supplied identifiers.

• Verification: Test authorized and unauthorized customer/tenant combinations.

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Priority Remediation Plan

1. Remove unrestricted command execution

This is the highest-risk capability and should be eliminated or replaced with tightly scoped operations.

2. Establish server-side authorization

Every privileged tool should enforce authorization independently of client claims.

3. Restrict filesystem access

Implement an explicit filesystem boundary and reject traversal or symlink escapes.

4. Restrict outbound networking

Prevent arbitrary destinations and apply network-level egress controls.

5. Reduce production-service privileges

The MCP server should operate with the minimum permissions required for its intended functions.

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Verification Plan

After remediation

1. Test every privileged tool with an unauthorized identity.
2. Test filesystem traversal and symlink escape attempts.
3. Test blocked internal/private network destinations.
4. Verify arbitrary shell commands cannot be executed.
5. Test cross-tenant customer-data access.
6. Confirm credentials are not returned through tool output or logs.
7. Re-run the complete MCP security audit.

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Production Decision

🔴 NOT READY FOR PRODUCTION

The unrestricted command execution capability alone represents a critical production risk. The server should not be deployed until the critical issue and authorization/network/filesystem risks have been remediated and independently verified.

Next action: Remediate the critical and high-priority findings, then perform a complete verification audit.