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 ini…
Published: 2026-07-31 · CVSS: 8.0 · CVSS 4.0
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.
Source: CVE Program · Revision 8b16575c39f1e1810c5e863010da073d2d3285e7