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CVE-2026-9739: MCP Toolbox for Databases vulnerable to DNS rebinding attacks

criticalCVSS 4.0 9.4GHSA-7pf3-8xx7-rvhf

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.

Published May 28, 2026 · Updated Jul 1, 2026

Affected packages

github.com/googleapis/mcp-toolbox

Ecosystem: Go
Affected: < 1.2.0
Fixed in: 1.2.0
Check: go list -m github.com/googleapis/mcp-toolbox

Advisory details

From the GitHub Advisory Database (CC BY 4.0).

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

How this page is made: the data panel comes from the GitHub Advisory Database, CISA’s KEV catalog, the NVD and FIRST EPSS, and updates twice a day. No analysis has been written for this entry yet. Methodology

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