PT-2026-50659 · Google · Mcp Toolbox For Databases

Published 2026-06-18 · Updated 2026-06-18 · CVE-2026-11717

Mitre

CVSS v4.0

9.3

Critical

Base vector

AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N

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.

Fix

Improper Authentication

Weakness Enumeration

CWE-287

Related Identifiers

CVE-2026-11717

Affected Products

Mcp Toolbox For Databases

References · 3

• https://nvd.nist.gov/vuln/detail/CVE-2026-11717 · Security Note
• https://github.com/googleapis/mcp-toolbox/pull/3341 · Note
• https://twitter.com/ptdbugs/status/2067629310077235322 · Twitter Post