CVE-2026-9739 (GCVE-0-2026-9739)

Vulnerability from cvelistv5 – Published: 2026-05-27 21:38 – Updated: 2026-05-28 13:20
VLAI
Summary
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.
Severity
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
CWE
  • CWE-942 - Permissive Cross-domain Policy with Untrusted Domains
Assigner
References
Impacted products
Vendor Product Version
Google MCP Toolbox for Databases Affected: 0 , < PR 3054 (Fix CORS bypass) (custom)
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Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.

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  • Seen: The vulnerability was mentioned, discussed, or observed by the user.
  • Confirmed: The vulnerability has been validated from an analyst's perspective.
  • Published Proof of Concept: A public proof of concept is available for this vulnerability.
  • Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
  • Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
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