CVE-2026-11717
CriticalCVSS 9.3Exploitation Probability (EPSS)
Low risk9th percentile — higher than 9% of all known CVEs
Summary
An authentication bypass vulnerability exists in the googleapis/mcp-toolbox that allows bypassing authentication. The issue is related to opaque token validation, where the absence of the 'active' key in the OAuth 2.0 introspection response results in the acceptance of tokens that should not be considered valid.
Risk Assessment
The organization may be exposed to unauthorized access to protected tools and data, potentially leading to serious security breaches.
Recommendation
It is recommended to update the googleapis/mcp-toolbox to the latest version that fixes token validation and to monitor access to protected resources.
Original NVD description (English source)
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.