VULNERABILITY INTELLIGENCE
CVE-2026-9739
EPSS probability0.28%
CISA KEVNot currently listed
Published2026-05-27
Last modified2026-10-26
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.
Weakness classification
- cve-coordination@google.com: CWE-942