{"id":"CVE-2026-14541","aliases":["EUVD-2026-51381","GHSA-656w-qf75-c5gf"],"status":"published","title":"Authentication Bypass and Audience Confusion in MCP Toolbox OAuth Provider","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":{"version":"4.0","score":8,"vector":"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","level":"high","assessor":"cna","from":"cve"},"epss":{"day":"2026-11-09","score":0.00253,"percentile":0.16845,"model":"v2026.06.15"},"facts":{"in_kev":false,"known_exploited":false,"public_exploit":false,"fix_available":false},"cwes":["CWE-287"],"published":"2026-07-31T01:48:39Z","modified":"2026-10-28T02:31:11Z","products":[{"vendor":"google","product":"mcp-toolbox"},{"vendor":"google","product":"mcp_toolbox_for_databases"}],"references":[{"url":"https://github.com/googleapis/mcp-toolbox/pull/3450","tags":["Issue Tracking","Patch","fix"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-14541","tags":["advisory"]},{"url":"https://github.com/advisories/GHSA-656w-qf75-c5gf"},{"url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/14xxx/CVE-2026-14541.json","tags":["advisory"]}],"sources":{"cve":[{"id":"CVE-2026-14541","title":"Authentication Bypass and Audience Confusion in MCP Toolbox OAuth Provider","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.","status":"published","published":"2026-07-31T01:48:39.019Z","modified":"2026-07-31T16:14:54.005Z","cvss":[{"version":"4.0","score":8,"vector":"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","level":"high","assessor":"cna"}],"cwes":["CWE-287"],"updated_at":"2026-11-02T13:38:32.13011Z"}],"euvd":[{"id":"EUVD-2026-51381","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.","status":"published","published":"2026-07-31T01:48:39Z","modified":"2026-07-31T16:14:54Z","cvss":[{"version":"4.0","score":8,"vector":"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","level":"high"}],"updated_at":"2026-11-02T18:02:25.856077Z"}],"ghsa":[{"id":"GHSA-656w-qf75-c5gf","title":"An authentication bypass and audience confusion vulnerability exists in the Google OAuth provider...","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.","status":"published","published":"2026-07-31T03:31:16Z","modified":"2026-08-08T00:32:15Z","cvss":[{"version":"4.0","score":8,"vector":"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/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X","level":"high"},{"version":"3.1","score":7.5,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N","level":"high"}],"cwes":["CWE-287"],"updated_at":"2026-11-02T15:10:12.306859Z"}],"nvd":[{"id":"CVE-2026-14541","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.","status":"published","published":"2026-07-31T03:16:24.17Z","modified":"2026-10-23T23:10:00.157Z","cvss":[{"version":"4.0","score":8,"vector":"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/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X","level":"high","assessor":"secondary"},{"version":"3.1","score":7.5,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N","level":"high","assessor":"primary"}],"cwes":["CWE-287"],"updated_at":"2026-11-02T14:12:33.955581Z"}],"osv":[{"id":"CVE-2026-14541","title":"Authentication Bypass and Audience Confusion in MCP Toolbox OAuth Provider","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.","status":"published","published":"2026-07-31T01:48:39.019Z","modified":"2026-10-28T02:31:11.635957677Z","cvss":[{"version":"4.0","score":8,"vector":"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","level":"high"}],"cwes":["CWE-287"],"updated_at":"2026-11-02T15:44:57.354194Z"}]}}