by Kastro
Paper/Archive/CVE-2026-9739

CVE-2026-9739

Google MCP Toolbox for Databases — Vulnerable to DNS rebinding attacks when using SSE (http://b/499408790).

EPSS 0.3%CVSS 9.4
critical.is priorityof 100
32
CVSS 9.4 (CNA)9.4 / 10 × 3028.2Not in CISA KEV+300.0EPSS percentile 20.4.204 × 204.1No public exploit+100.0SSVC exploitation: none+100.0
Description · from the CVE record

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.

Affected

ProductAffectedFixed inSource
MCP Toolbox for Databases< PR 3054 (Fix CORS bypass)PR 3054 (Fix CORS bypass)CNA

Scores by source

Google (CNA)9.4CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:A/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H
CISA ADPSSVCExploitation: none · Automatable: no · Technical impact: total

References

refgithub.com/googleapis/mcp-toolbox/issues/3053refgithub.com/googleapis/mcp-toolbox/pull/3054