CVE-2026-11718

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However, the subsequent claim-checking logic (validateClaims) evaluates the issuer condition as if a.issuer != \"\" && iss != \"\". If the external OAuth provider's introspection response omits the optional iss (issuer) field completely, the variable iss defaults to an empty string. This causes the conditional block to evaluate to false and be skipped silently. Consequently, the application accepts tokens issued by unauthorized or unintended third-party identity providers."}, {"lang": "es", "value": "Una vulnerabilidad de omisi\u00f3n de autenticaci\u00f3n existe en la ruta gen\u00e9rica de validaci\u00f3n de tokens opacos (validateOpaqueToken) de googleapis/mcp-toolbox.\n\nCuando la caja de herramientas valida un token opaco a trav\u00e9s de un endpoint de introspecci\u00f3n de OAuth 2.0 (RFC 7662), decodifica la respuesta en una estructura introspectResp. Sin embargo, la l\u00f3gica subsiguiente de verificaci\u00f3n de reclamaciones (validateClaims) eval\u00faa la condici\u00f3n del emisor como si a.issuer != \u201c\u201d && iss != \u201c\u201d. Si la respuesta de introspecci\u00f3n del proveedor OAuth externo omite completamente el campo opcional iss (emisor), la variable iss por defecto es una cadena vac\u00eda. Esto provoca que el bloque condicional se eval\u00fae como falso y se omita silenciosamente. En consecuencia, la aplicaci\u00f3n acepta tokens emitidos por proveedores de identidad de terceros no autorizados o no previstos."}], "id": "CVE-2026-11718", "lastModified": "2026-10-26T11:10:00.157", "metrics": {"cvssMetricV31": [{"cvssData": {"attackComplexity": "LOW", "attackVector": "NETWORK", "availabilityImpact": "NONE", "baseScore": 9.1, "baseSeverity": "CRITICAL", "confidentialityImpact": "HIGH", "integrityImpact": "HIGH", "privilegesRequired": "NONE", "scope": "UNCHANGED", "userInteraction": "NONE", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N", "version": "3.1"}, "exploitabilityScore": 3.9, "impactScore": 5.2, "source": "nvd@nist.gov", "type": "Primary"}], "cvssMetricV40": [{"cvssData": {"Automatable": "NOT_DEFINED", "Recovery": "NOT_DEFINED", "Safety": "NOT_DEFINED", "attackComplexity": "LOW", "attackRequirements": "NONE", "attackVector": "NETWORK", "availabilityRequirement": "NOT_DEFINED", "baseScore": 9.3, "baseSeverity": "CRITICAL", "confidentialityRequirement": "NOT_DEFINED", "exploitMaturity": "NOT_DEFINED", "integrityRequirement": "NOT_DEFINED", "modifiedAttackComplexity": "NOT_DEFINED", "modifiedAttackRequirements": "NOT_DEFINED", "modifiedAttackVector": "NOT_DEFINED", "modifiedPrivilegesRequired": "NOT_DEFINED", "modifiedSubAvailabilityImpact": "NOT_DEFINED", "modifiedSubConfidentialityImpact": "NOT_DEFINED", "modifiedSubIntegrityImpact": "NOT_DEFINED", "modifiedUserInteraction": "NOT_DEFINED", "modifiedVulnAvailabilityImpact": "NOT_DEFINED", "modifiedVulnConfidentialityImpact": "NOT_DEFINED", "modifiedVulnIntegrityImpact": "NOT_DEFINED", "privilegesRequired": "NONE", "providerUrgency": "NOT_DEFINED", "subAvailabilityImpact": "NONE", "subConfidentialityImpact": "NONE", "subIntegrityImpact": "NONE", "userInteraction": "NONE", "valueDensity": "NOT_DEFINED", "vectorString": "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:X/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", "version": "4.0", "vulnAvailabilityImpact": "NONE", "vulnConfidentialityImpact": "HIGH", "vulnIntegrityImpact": "HIGH", "vulnerabilityResponseEffort": "NOT_DEFINED"}, "source": "cve-coordination@google.com", "type": "Secondary"}], "ssvcV203": [{"source": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "ssvcData": {"id": "CVE-2026-11718", "options": [{"exploitation": "none"}, {"automatable": "yes"}, {"technicalImpact": "total"}], "role": "CISA Coordinator", "timestamp": "2026-06-18T13:01:08.666194Z", "version": "2.0.3"}}]}, "published": "2026-06-18T14:17:20.190", "references": [{"source": "cve-coordination@google.com", "tags": ["Patch"], "url": "https://github.com/googleapis/mcp-toolbox/pull/3360"}], "sourceIdentifier": "cve-coordination@google.com", "vulnStatus": "Analyzed", "weaknesses": [{"description": [{"lang": "en", "value": "CWE-287"}], "source": "cve-coordination@google.com", "type": "Secondary"}]}

{}

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