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.
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References
| Link | Providers |
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| https://github.com/googleapis/mcp-toolbox/pull/3450 |
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History
Fri, 31 Jul 2026 17:30:00 +0000
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ssvc
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Fri, 31 Jul 2026 03:00:00 +0000
| Type | Values Removed | Values Added |
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| 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. | |
| Title | Authentication Bypass and Audience Confusion in MCP Toolbox OAuth Provider | |
| Weaknesses | CWE-287 | |
| References |
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| Metrics |
cvssV4_0
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Status: PUBLISHED
Assigner: Google
Published:
Updated: 2026-07-31T16:14:54.005Z
Reserved: 2026-07-03T03:38:02.749Z
Link: CVE-2026-14541
Updated: 2026-07-31T16:14:50.559Z
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