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VULNERABILITIES

CVE-2026-9739 Details

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.

Metrics

CVSS 3.x Severity and Vector Strings:

No CVSS 3.x data is available for this CVE.

References to Advisories, Solutions, and Tools

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URLSource(s)Tag(s)
https://github.com/googleapis/mcp-toolbox/issues/3053 [email protected]
https://github.com/googleapis/mcp-toolbox/pull/3054 [email protected]

Weakness Enumeration

CWE-IDCWE NameSource
CWE-942Permissive Cross-domain Policy with Untrusted Domains[email protected]

Affected Products

No affected product data is available for this CVE.

Change History

3 change records found show changes

QUICK INFO

CVE Dictionary Entry:
CVE-2026-9739
NVD Published Date:
May 27, 2026
NVD Last Modified:
Jun 17, 2026
Source:
[email protected]
CVE-2026-9739 Details - Not Deferred