Vulnerability · Published Jun 18, 2026 · Assigned by Google
CVE-2026-11717
Critical 9.3
In plain English
A critical-severity improper authentication in MCP Toolbox for Databases (googleapis/mcp-toolbox) from Google. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.2% (higher than 7% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.
Official 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.
Affected packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| Go | github.com/googleapis/mcp-toolbox | 1.4.0 | GHSA-8fcc-w5hv-4gxv |
| Go | github.com/googleapis/mcp-toolbox | 1.4.0 | GO-2026-5251 |
Affected products (as reported)
| Vendor | Product | Versions |
|---|---|---|
| MCP Toolbox for Databases (googleapis/mcp-toolbox) | 1.0.0 – through 1.3.0 |
Weakness: CWE-287 · Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N