CVE-2026-14541 – Authentication Bypass and Audience Confusion in MCP Toolbox OAuth Provider

CVE ID :CVE-2026-14541

Published : July 31, 2026, 3:16 a.m. | 29 minutes ago

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.

Severity: 8.0 | HIGH

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