CVEvulnerability

CVE-2026-9739

9.4 CRITICAL Published 2026-05-27 Modified 2026-10-26 Official page ↗
Status
Awaiting Analysis
Published
2026-05-27
Last modified
2026-10-26
Assigner
[email protected]
CVSS 4.0 ([email protected])
9.4 CRITICAL — 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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
Weaknesses
CWE-942

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.

Related

Weakness · CWE (1)

  • CWE-942 Permissive Cross-domain Security Policy with Untrusted Domains weakness

References