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.

Score
CVSS 4.0 9.4 Critical
Status
Awaiting Analysis - cve-coordination@google.com
Published
2026-05-27
Last modified
2026-10-26
Weaknesses
CWE-942

Affected products

References

 
 
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