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.
History

Thu, 28 May 2026 14:15:00 +0000

Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'none', 'Technical Impact': 'total'}, 'version': '2.0.3'}


Thu, 28 May 2026 00:45:00 +0000

Type Values Removed Values Added
Title DNS Rebinding via SSE Causing CORS Bypass in MCP Toolbox for Databases

Wed, 27 May 2026 22:30:00 +0000

Type Values Removed Values Added
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.
Weaknesses CWE-942
References
Metrics cvssV4_0

{'score': 9.4, 'vector': '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'}


cve-icon MITRE

Status: PUBLISHED

Assigner: Google

Published: 2026-05-27T21:38:55.833Z

Updated: 2026-05-28T13:20:43.816Z

Reserved: 2026-05-27T17:31:41.604Z

Link: CVE-2026-9739

cve-icon Vulnrichment

Updated: 2026-05-28T13:19:59.632Z

cve-icon NVD

Status : Received

Published: 2026-05-27T23:16:48.573

Modified: 2026-05-27T23:16:48.573

Link: CVE-2026-9739

cve-icon Redhat

No data.