CVE-2026-14541: Authentication Bypass and Audience Confusion in MCP Toolbox OAuth Provider
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.
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Upgrade
Upgrade
Google mcp-toolbox OAuth provider (Google OAuth provider component)to a version that resolves this vulnerability.Fixed in 1.4.0 - Configuration
Ensure the Google authService is initialized with an explicitly defined audience and/or clientId (e.g., set both) so the ValidateMCPAuth pipeline does not skip audience validation for opaque tokens when mcpEnabled: true.
Google mcp-toolbox (Google authService) audience/clientId for authService = explicitly define
Event History
Frequently Asked Questions
What is the severity of CVE-2026-14541?
The severity of CVE-2026-14541 is rated at 71, indicating a significant security concern.
What types of systems are affected by CVE-2026-14541?
CVE-2026-14541 affects Google mcp-toolbox version 1.4.0 when improperly configured.
How do I fix CVE-2026-14541?
To fix CVE-2026-14541, ensure that the Google authService is initialized with properly defined audience and clientId parameters.
What is the impact of CVE-2026-14541?
The impact of CVE-2026-14541 is an authentication bypass that could allow unauthorized access to system resources.
When was CVE-2026-14541 published?
CVE-2026-14541 was published on July 31, 2026.