He Wei（ギカク）

A Server-Side Request Forgery (SSRF) and credential exfiltration vulnerability exists in the cloud-healthcare-fhir-fetch-page tool of googleapis/mcp-toolbox. The tool takes an unvalidated pageURL parameter from the client and issues an HTTP GET request to it using an authenticated client. The underlying transport automatically attaches an Authorization: Bearer header to every outbound request regardless of the destination host. An attacker can supply an arbitrary external URL to the pageURL parameter (either directly via the tool execution payload or implicitly via data-driven pagination tracking loops), leading Toolbox into sending its OAuth/service-account access token to an attacker-controlled listener. Depending on the configuration, this leaks either the end-user's token or the broader service-account access token (ADC), potentially exposing Protected Health Information (PHI) and secondary Google Cloud Platform services.

**Name of the Vulnerable Software and Affected Versions** MCP Toolbox for Databases (affected versions not specified) **Description** An authenticated authorization bypass occurs due to missing scope enforcement in older protocol handlers. While the 2025-11-25 protocol version handler correctly enforces per-tool restrictions defined by `scopesRequired`, older supported versions (2025-06-18, 2025-03-26, and 2024-11-05) do not perform this check. An authenticated client with low-privilege tokens can bypass these 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 the server to the 2024-11-05 handler. **Recommendations** At the moment, there is no information about a newer version that contains a fix for this vulnerability.