CVE-2026-14541 Authentication Bypass and Audience Confusion in MCP Toolbox OAuth Provider
Attackers can bypass authentication in Google MCP Toolbox by using unrelated OAuth tokens when audience validation is skipped due to missing configuration.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- None listed
What is CVE-2026-14541?
CVE-2026-14541 is a high-severity authentication bypass vulnerability in Google mcp-toolbox, published on 31 Jul 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
An authentication bypass and audience confusion vulnerability exists in the Google OAuth provider component of Google mcp-toolbox version 1.4.0. When a Google authService is initialized with mcpEnabled: true but lacks an explicitly defined audience or clientId, the ValidateMCPAuth pipeline for opaque tokens skips audience validation entirely. As a result, the toolbox will accept any valid Google OAuth access token—even those minted for unrelated ecosystem applications—granting unauthorized clients access to protected tools and data backends.
Weakness: CWE-287
Which versions are affected by CVE-2026-14541?
It affects 1 product.
Products include Google Mcp Toolbox for Databases.
How do I fix CVE-2026-14541?
No fix has been published for CVE-2026-14541 yet. Limit exposure of the affected software until one is available.
Upgrade, and rotate credentials and sessions that may have been exposed. More about Authentication bypass.
Is CVE-2026-14541 being exploited?
There is no known exploitation of CVE-2026-14541 in the wild and no public exploit code.
Other vulnerabilities in Google mcp-toolbox
- CVE-2026-11720 Path Traversal in googleapis/mcp-toolbox HTTP Tool URL Builder
- CVE-2026-11717 googleapis/mcp-toolbox: authentication bypass vulnerability in the generic opaque token validation path (validateOpaqueToken)
- 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
Sources
Also known as GHSA-656w-qf75-c5gf.