MCP Toolbox for Databases vulnerable to DNS rebinding attacks
Date: 2026-05
Affected: go/github.com/googleapis/mcp-toolbox
Attack vector: other
Category: vulnerability-disclosure
Severity: Critical
CVE: CVE-2026-9739
CWE: CWE-942

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.


Mitigations:

Architectural layers (MAESTRO):