Description
An authenticated authorization bypass vulnerability exists in MCP Toolbox for Databases due to missing scope enforcement across older protocol handlers. While the 2025-11-25 protocol version handler correctly enforces per-tool restrictions defined by scopesRequired, older supported protocol versions (2025-06-18, 2025-03-26, and 2024-11-05) omit this check. An authenticated client with low-privilege tokens (e.g., read) can bypass the intended per-tool scope restrictions and execute high-privilege tools (e.g., admin) simply by specifying an older protocol version in the MCP-Protocol-Version header, or by omitting the header entirely (which causes the server to default to the vulnerable 2024-11-05 handler).
Problem types
CWE-862: Missing Authorization
Product status
1.3.0
Credits
HE WEI（ギカク）(https://www.linkedin.com/in/gikaku/)
References
github.com/googleapis/mcp-toolbox/pull/3335
github.com/googleapis/mcp-toolbox/pull/3049