CVE-2026-9739
Google LLC · published 2026-05-27
Source record Collected from the National Vulnerability Database (NVD)
Description
Description by Google Inc. via the CVE Program.
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.
Status at the source
- NVD status: Awaiting Analysis — NVD has not analysed this CVE.
Affected products, as the source lists them
| Vendor | Product | Versions |
|---|---|---|
| MCP Toolbox for Databases | 0 – before PR 3054 (Fix CORS bypass): affected |
DeSpy has not checked any unit, hardware revision or firmware. A product missing here is not a statement that it is unaffected.
Scores, as their sources published them
- CVSS 4.0: 9.4 CRITICAL — as published by Google Inc. (Secondary)
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 - SSVC — CISA's assessment (SSVC 2.0.3, CISA Coordinator): Exploitation: none · Automatable: no · Technical impact: total
DeSpy does not score records. These are the sources' own values.
Weaknesses
Sources
References the source lists
- https://github.com/googleapis/mcp-toolbox/issues/3053
- https://github.com/googleapis/mcp-toolbox/pull/3054
Source dates: published 2026-05-27, last changed 2026-06-17. DeSpy's copy of this version is dated 2026-09-28.
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