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.

CVSS v3 9.1 CRITICAL

9.1^/10

CVSS v3 : CRITICAL

Vector :

Exploitability : 3.9 / Impact : 5.2

Attack Vector NETWORK

Attack Complexity LOW

Privileges Required NONE

User Interaction NONE

Confidentiality Impact HIGH

Integrity Impact HIGH

Availability Impact NONE

Scope UNCHANGED

References

Link	Resource
https://github.com/googleapis/mcp-toolbox/pull/3341	Patch Third Party Advisory

Configurations

Configuration 1 (hide)

cpe:2.3:a:google:mcp_toolbox_for_databases:*:*:*:*:*:*:*:*

History

No history.

Information

Published : 2026-06-18 14:17

Updated : 2026-08-17 16:13

NVD link : CVE-2026-11717

Mitre link : CVE-2026-11717

CVE.ORG link : CVE-2026-11717

JSON object : View

Products Affected

google

mcp_toolbox_for_databases

CWE

CWE-287

Improper Authentication

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