{"id":"CVE-2026-9739","sourceIdentifier":"cve-coordination@google.com","published":"2026-05-27T23:16:48.573","lastModified":"2026-10-26T12:10:00.130","vulnStatus":"Awaiting Analysis","cveTags":[],"descriptions":[{"lang":"en","value":"Vulnerable to DNS rebinding attacks when using SSE (http://b/499408790). During the beta phase, we implemented `allowed-origins` and `allowed-hosts` flags to align with MCP security guidelines. However, the hardcoded `Access-Control-Allow-Origin: *` header in the SSE initialization handler was inadvertently retained. This vulnerability specifically impacts users connecting via Toolbox using SSE under specification v2024-11-05."},{"lang":"es","value":"Vulnerable a ataques de DNS rebinding al usar SSE (http://b/499408790). Durante la fase beta, implementamos las banderas ’allowed-origins’ y ’allowed-hosts’ para alinearnos con las directrices de seguridad de MCP. Sin embargo, el encabezado ’Access-Control-Allow-Origin: *’ codificado de forma rígida en el gestor de inicialización de SSE se retuvo inadvertidamente. Esta vulnerabilidad impacta específicamente a los usuarios que se conectan a través de Toolbox usando SSE bajo la especificación v2024-11-05."}],"affected":[{"source":"cve-coordination@google.com","affectedData":[{"vendor":"Google","product":"MCP Toolbox for Databases","defaultStatus":"unaffected","versions":[{"version":"0","lessThan":"PR 3054 (Fix CORS bypass)","versionType":"custom","status":"affected"}]}]}],"metrics":{"cvssMetricV40":[{"source":"cve-coordination@google.com","type":"Secondary","cvssData":{"version":"4.0","vectorString":"CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:A/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H/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","baseScore":9.4,"baseSeverity":"CRITICAL","attackVector":"NETWORK","attackComplexity":"LOW","attackRequirements":"NONE","privilegesRequired":"NONE","userInteraction":"ACTIVE","vulnConfidentialityImpact":"HIGH","vulnIntegrityImpact":"HIGH","vulnAvailabilityImpact":"HIGH","subConfidentialityImpact":"HIGH","subIntegrityImpact":"HIGH","subAvailabilityImpact":"HIGH","exploitMaturity":"NOT_DEFINED","confidentialityRequirement":"NOT_DEFINED","integrityRequirement":"NOT_DEFINED","availabilityRequirement":"NOT_DEFINED","modifiedAttackVector":"NOT_DEFINED","modifiedAttackComplexity":"NOT_DEFINED","modifiedAttackRequirements":"NOT_DEFINED","modifiedPrivilegesRequired":"NOT_DEFINED","modifiedUserInteraction":"NOT_DEFINED","modifiedVulnConfidentialityImpact":"NOT_DEFINED","modifiedVulnIntegrityImpact":"NOT_DEFINED","modifiedVulnAvailabilityImpact":"NOT_DEFINED","modifiedSubConfidentialityImpact":"NOT_DEFINED","modifiedSubIntegrityImpact":"NOT_DEFINED","modifiedSubAvailabilityImpact":"NOT_DEFINED","Safety":"NOT_DEFINED","Automatable":"NOT_DEFINED","Recovery":"NOT_DEFINED","valueDensity":"NOT_DEFINED","vulnerabilityResponseEffort":"NOT_DEFINED","providerUrgency":"NOT_DEFINED"}}],"ssvcV203":[{"source":"134c704f-9b21-4f2e-91b3-4a467353bcc0","ssvcData":{"timestamp":"2026-05-28T13:19:37.204820Z","id":"CVE-2026-9739","options":[{"exploitation":"none"},{"automatable":"no"},{"technicalImpact":"total"}],"role":"CISA Coordinator","version":"2.0.3"}}]},"weaknesses":[{"source":"cve-coordination@google.com","type":"Secondary","description":[{"lang":"en","value":"CWE-942"}]}],"references":[{"url":"https://github.com/googleapis/mcp-toolbox/issues/3053","source":"cve-coordination@google.com"},{"url":"https://github.com/googleapis/mcp-toolbox/pull/3054","source":"cve-coordination@google.com"}]}