CVE-2026-11717 googleapis/mcp-toolbox: authentication bypass vulnerability in the generic opaque token validation path (validateOpaqueToken)
Attackers can bypass authentication in MCP Toolbox by sending tokens that omit the active field, gaining unauthorized access to protected tools and data sources.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-11717?
CVE-2026-11717 is a critical authentication bypass vulnerability in MCP Toolbox for Databases (googleapis/mcp-toolbox), published on 18 Jun 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
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.
Weakness: CWE-287
Which versions are affected by CVE-2026-11717?
3 open source packages ship an affected version, including github.com/googleapis/mcp-toolbox. It affects 1 product.
| Package | Affected | Fixed in |
|---|---|---|
github.com/googleapis/mcp-toolbox Go | All versions | 1.4.0 |
github.com/googleapis/mcp-toolbox Go | All versions | 1.4.0 |
github.com/googleapis/mcp-toolbox Go | All versions | 1.4.0 |
Products include Google Mcp Toolbox for Databases.
How do I fix CVE-2026-11717?
Upgrade github.com/googleapis/mcp-toolbox to 1.4.0 or later.
Upgrade, and rotate credentials and sessions that may have been exposed. More about Authentication bypass.
Is CVE-2026-11717 being exploited?
There is no known exploitation of CVE-2026-11717 in the wild and no public exploit code.
Other vulnerabilities in MCP Toolbox for Databases (googleapis/mcp-toolbox)
- CVE-2026-11720 Path Traversal in googleapis/mcp-toolbox HTTP Tool URL Builder
- CVE-2026-11718 googleapis/mcp-toolbox: authentication bypass vulnerability in the generic opaque token validation path (validateOpaqueToken)
- CVE-2026-15829 SQL Injection and Security Boundary Bypass in googleapis/mcp-toolbox
- CVE-2026-11719 MCP Toolbox for Databases: authenticated authorization bypass
- CVE-2026-14537 Authorization Bypass in MCP Toolbox Legacy HTTP Endpoints
Sources
Also known as GHSA-8fcc-w5hv-4gxv, GO-2026-5251.