CVE-2026-9739

CRITICAL

Google Mcp Toolbox For Databases - Permissive Cross-domain Security Policy with Untrusted Domains

Title source: rule

Description

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 (2)

Core 2

Core References

https://github.com/googleapis/mcp-toolbox/issues/3053

https://github.com/googleapis/mcp-toolbox/pull/3054

Scores

CVSS v4 9.4

EPSS 0.0018

EPSS Percentile 7.6%

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

CISA SSVC

Vulnrichment

Exploitation none

Automatable no

Technical Impact total

Details

CWE

CWE-942

Status published

Products (1)

Google/MCP Toolbox for Databases < PR 3054 (Fix CORS bypass)

Published May 27, 2026

Tracked Since May 28, 2026