{ "dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": { "cveId": "CVE-2026-9739", "assignerOrgId": "14ed7db2-1595-443d-9d34-6215bf890778", "state": "PUBLISHED", "assignerShortName": "Google", "dateReserved": "2026-05-27T17:31:41.604Z", "datePublished": "2026-05-27T21:38:55.833Z", "dateUpdated": "2026-05-28T13:20:43.816Z" }, "containers": { "cna": { "providerMetadata": { "orgId": "14ed7db2-1595-443d-9d34-6215bf890778", "shortName": "Google", "dateUpdated": "2026-05-27T21:38:55.833Z" }, "problemTypes": [ { "descriptions": [ { "lang": "en", "cweId": "CWE-942", "description": "CWE-942: Permissive Cross-domain Policy with Untrusted Domains", "type": "CWE" } ] } ], "impacts": [ { "capecId": "CAPEC-275", "descriptions": [ { "lang": "en", "value": "CAPEC-275: DNS Rebinding" } ] } ], "affected": [ { "vendor": "Google", "product": "MCP Toolbox for Databases", "versions": [ { "status": "affected", "version": "0", "lessThan": "PR 3054 (Fix CORS bypass)", "versionType": "custom" } ], "defaultStatus": "unaffected" } ], "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.", "supportingMedia": [ { "type": "text/html", "base64": false, "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." } ] } ], "references": [ { "url": "https://github.com/googleapis/mcp-toolbox/issues/3053" }, { "url": "https://github.com/googleapis/mcp-toolbox/pull/3054" } ], "metrics": [ { "format": "CVSS", "scenarios": [ { "lang": "en", "value": "GENERAL" } ], "cvssV4_0": { "attackVector": "NETWORK", "attackComplexity": "LOW", "attackRequirements": "NONE", "privilegesRequired": "NONE", "userInteraction": "ACTIVE", "vulnConfidentialityImpact": "HIGH", "subConfidentialityImpact": "HIGH", "vulnIntegrityImpact": "HIGH", "subIntegrityImpact": "HIGH", "vulnAvailabilityImpact": "HIGH", "subAvailabilityImpact": "HIGH", "exploitMaturity": "NOT_DEFINED", "Safety": "NOT_DEFINED", "Automatable": "NOT_DEFINED", "Recovery": "NOT_DEFINED", "valueDensity": "NOT_DEFINED", "vulnerabilityResponseEffort": "NOT_DEFINED", "providerUrgency": "NOT_DEFINED", "version": "4.0", "baseSeverity": "CRITICAL", "baseScore": 9.4, "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" } } ], "source": { "discovery": "UNKNOWN" }, "x_generator": { "engine": "Vulnogram 1.0.2" } }, "adp": [ { "metrics": [ { "other": { "type": "ssvc", "content": { "timestamp": "2026-05-28T13:19:37.204820Z", "id": "CVE-2026-9739", "options": [ { "Exploitation": "none" }, { "Automatable": "no" }, { "Technical Impact": "total" } ], "role": "CISA Coordinator", "version": "2.0.3" } } } ], "title": "CISA ADP Vulnrichment", "providerMetadata": { "orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "shortName": "CISA-ADP", "dateUpdated": "2026-05-28T13:20:43.816Z" } } ] } }