Executive Summary

This vulnerability is an authenticated authorization bypass in MCP Toolbox for Databases caused by missing scope enforcement in older protocol handlers.

While the latest protocol version (2025-11-25) correctly enforces per-tool scope restrictions, older supported versions (2025-06-18, 2025-03-26, and 2024-11-05) do not perform this check.

As a result, an authenticated client with low-privilege tokens can bypass intended restrictions and execute high-privilege tools by specifying an older protocol version in the MCP-Protocol-Version header or by omitting the header, which defaults to the vulnerable older handler.

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Impact Analysis

This vulnerability allows an authenticated user with low privileges to bypass authorization controls and gain access to high-privilege tools.

Such unauthorized access can lead to misuse or manipulation of database tools that should be restricted, potentially compromising the security and integrity of the system.

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Detection Guidance

This vulnerability can be detected by monitoring MCP protocol version headers in requests to the MCP Toolbox for Databases. Specifically, look for requests that specify older protocol versions (2024-11-05, 2025-03-26, 2025-06-18) or omit the MCP-Protocol-Version header, which defaults to the vulnerable 2024-11-05 handler.

You can detect potential exploitation attempts by capturing and analyzing network traffic or server logs for requests with these older protocol versions or missing headers.

• Use network packet capture tools (e.g., tcpdump, Wireshark) to filter for MCP protocol traffic and inspect the MCP-Protocol-Version header.
• Example tcpdump command to capture MCP traffic: tcpdump -i <interface> -A 'tcp port <MCP_port>'
• Use grep or similar tools on server logs to find requests with older or missing MCP-Protocol-Version headers, e.g., grep -E 'MCP-Protocol-Version: (2024-11-05|2025-03-26|2025-06-18)?' /path/to/logfile

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Mitigation Strategies

Immediate mitigation involves ensuring that all MCP protocol handlers enforce proper scope validation consistently across all supported protocol versions.

Upgrade the MCP Toolbox for Databases to version 1.4.0 or later, which includes the fix that centralizes and enforces scope validation across all protocol versions, preventing authorization bypass.

If upgrading immediately is not possible, consider blocking or rejecting requests that specify older MCP protocol versions (2024-11-05, 2025-03-26, 2025-06-18) or that omit the MCP-Protocol-Version header.

Review and audit authentication tokens and their scopes to ensure that low-privilege tokens cannot be used to execute high-privilege tools.

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Compliance Impact

The vulnerability allows an authenticated client with low-privilege tokens to bypass intended per-tool scope restrictions and execute high-privilege tools by exploiting older protocol versions that do not enforce scope validation properly.

Such an authorization bypass could lead to unauthorized access to sensitive data or administrative functions, potentially violating access control requirements mandated by common standards and regulations such as GDPR and HIPAA.

However, the provided context and resources do not explicitly discuss or analyze the impact of this vulnerability on compliance with these or other regulations.

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