CVE-2026-11717: CWE-287: Improper Authentication in Google MCP Toolbox for Databases (googleapis/mcp-toolbox)
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.
AI Analysis
Technical Summary
The vulnerability exists in the validateOpaqueToken function of googleapis/mcp-toolbox version 1.0.0. When an OAuth 2.0 introspection endpoint response omits the mandatory 'active' boolean field, the internal check that rejects inactive tokens is bypassed because the 'active' field pointer remains nil. The code only rejects tokens explicitly marked as inactive (active=false). If the 'active' field is missing, the token is accepted, resulting in an authentication bypass that grants unauthorized access to protected resources.
Potential Impact
An attacker can gain unauthorized access to the MCP Toolbox for Databases by presenting tokens that lack the 'active' field in the introspection response. This bypasses authentication controls, potentially exposing sensitive tools and data sources without valid authorization.
Mitigation Recommendations
Patch status is not yet confirmed — check the vendor advisory for current remediation guidance. No official fix or workaround has been published at this time. Users should monitor Google’s advisories for updates and apply patches once available.
CVE-2026-11717: CWE-287: Improper Authentication in Google MCP Toolbox for Databases (googleapis/mcp-toolbox)
Description
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 v4.0
Score 9.3critical
Affected software
pkg:github/googleapis/mcp-toolboxRun on your own infrastructure? Check whether these packages are installed with threat-finder — our free open-source scanner.
Weaknesses
AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
The vulnerability exists in the validateOpaqueToken function of googleapis/mcp-toolbox version 1.0.0. When an OAuth 2.0 introspection endpoint response omits the mandatory 'active' boolean field, the internal check that rejects inactive tokens is bypassed because the 'active' field pointer remains nil. The code only rejects tokens explicitly marked as inactive (active=false). If the 'active' field is missing, the token is accepted, resulting in an authentication bypass that grants unauthorized access to protected resources.
Potential Impact
An attacker can gain unauthorized access to the MCP Toolbox for Databases by presenting tokens that lack the 'active' field in the introspection response. This bypasses authentication controls, potentially exposing sensitive tools and data sources without valid authorization.
Mitigation Recommendations
Patch status is not yet confirmed — check the vendor advisory for current remediation guidance. No official fix or workaround has been published at this time. Users should monitor Google’s advisories for updates and apply patches once available.
Technical Details
- Data Version
- 5.2
- Assigner Short Name
- Date Reserved
- 2026-06-09T00:41:54.835Z
- Cvss Version
- 4.0
- State
- PUBLISHED
- Remediation Level
- null
Threat ID: 6a33df14f198dc38c1c0ed57
Added to database: 6/18/2026, 12:05:40 PM
Last enriched: 6/18/2026, 12:20:12 PM
Last updated: 6/18/2026, 1:10:44 PM
Views: 3
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