Vulnerability Details CVE-2026-11717
An authentication bypass vulnerability exists in the generic opaque token validation path (validateOpaqueToken) of googleapis/mcp-toolbox.
When verifying an unparsed opaque token via an OAuth 2.0 introspection endpoint (RFC 7662), the toolbox decodes the response into an introspectResp struct where the Active field is declared as a pointer to a boolean (*bool). The code only explicitly rejects a token if the response contains a populated active field set to false (if introspectResp.Active != nil && !*introspectResp.Active). If an introspection endpoint responds with a payload that completely omits the mandatory active key, the internal variable remains nil, causing the conditional check to short-circuit. As a result, Toolbox accepts authorization tokens missing the "active" field, granting access to protected tools and underlying data sources.
Exploit prediction scoring system (EPSS) score
EPSS Score 0.002
EPSS Ranking 7.2%
CVSS Severity
CVSS v3 Score 9.1
Products affected by CVE-2026-11717
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cpe:2.3:a:google:mcp_toolbox_for_databases:1.0.0
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cpe:2.3:a:google:mcp_toolbox_for_databases:1.1.0
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cpe:2.3:a:google:mcp_toolbox_for_databases:1.2.0
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cpe:2.3:a:google:mcp_toolbox_for_databases:1.3.0