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.
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History
Thu, 28 May 2026 14:15:00 +0000
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ssvc
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Thu, 28 May 2026 00:45:00 +0000
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| Title | DNS Rebinding via SSE Causing CORS Bypass in MCP Toolbox for Databases |
Wed, 27 May 2026 22:30:00 +0000
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| 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. | |
| Weaknesses | CWE-942 | |
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cvssV4_0
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Status: PUBLISHED
Assigner: Google
Published: 2026-05-27T21:38:55.833Z
Updated: 2026-05-28T13:20:43.816Z
Reserved: 2026-05-27T17:31:41.604Z
Link: CVE-2026-9739
Updated: 2026-05-28T13:19:59.632Z
Status : Received
Published: 2026-05-27T23:16:48.573
Modified: 2026-05-27T23:16:48.573
Link: CVE-2026-9739
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