CVE-2026-9739

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.

CVSS

No CVSS.

References

Link	Resource
https://github.com/googleapis/mcp-toolbox/issues/3053
https://github.com/googleapis/mcp-toolbox/pull/3054

Configurations

No configuration.

History

27 May 2026, 23:16

Type	Values Removed	Values Added
New CVE

Information

Published : 2026-05-27 23:16

Updated : 2026-05-29 15:42

NVD link : CVE-2026-9739

Mitre link : CVE-2026-9739

CVE.ORG link : CVE-2026-9739

JSON object : View

Products Affected

No product.

CWE

CWE-942

Permissive Cross-domain Policy with Untrusted Domains

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CVE-2026-9739

JSON object

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