CVE-2026-14541: high-severity vulnerability in Google mcp-toolbox
Authentication Bypass and Audience Confusion in MCP Toolbox OAuth Provider
Published
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21Vexday Risk Score
No sign of exploitation. No public exploitation artifact known so far.
ssvc Trackcvss 8epss 0.3%
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.
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N/E:U
Affected products
Google · mcp-toolboxRelated CVEs — Google mcp-toolbox
In the same product, most dangerous first.
CVE-2026-14537HIGHAuthorization Bypass in MCP Toolbox Legacy HTTP EndpointsEPSS 0.3%CVE-2026-14539MEDIUMDenial of Service via Unrestricted Payload Buffering in MCP ToolboxEPSS 0.2%CVE-2026-14538MEDIUMBigQuery Dataset Allowlist Bypass via Metadata Dry-Run in MCP ToolboxEPSS 0.2%CVE-2026-14540HIGHServer-Side Request Forgery via Unrestricted HTTP Redirection in MCP ToolboxEPSS 0.1%