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CVE-2026-9739 — Vulnerability in github.com/googleapis/mcp-toolbox...

CRITICAL

MCP Toolbox for Databases vulnerable to DNS rebinding attacks

Published May 28, 2026Updated July 7, 2026Source: osv

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.

Advisory Timeline

  • First published May 28, 2026 (137 days ago).
  • Last revised July 7, 2026 — 41 days after initial publication.

Remediation

Upgrade to the fixed version using your package manager.

Go
Update github.com/googleapis/mcp-toolbox to 1.2.0 or later
go get github.com/googleapis/mcp-toolbox@v1.2.0

After upgrading, run your dependency scanner again to confirm the vulnerability is resolved.

Affected Packages (1)

Affects 1 ecosystem: go (1).

PackageEcosystemAffectedFixed In
github.com/googleapis/mcp-toolbox
go
All versions1.2.0

Vulnerability Classification

Common Weakness Enumeration (CWE) identifiers for this vulnerability type.

CVSS Score Breakdown

What the CVSS (Common Vulnerability Scoring System) 9.1 score means for each attack dimension.

Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
A
Scope
—
Confidentiality
—
Integrity
—
Availability
—

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

References

Frequently Asked Questions

What is CVE-2026-9739?
MCP Toolbox for Databases vulnerable to DNS rebinding attacks This vulnerability has been assigned a severity rating of CRITICAL (CVSS score: 9.1/10).
How do I check if my project is affected by CVE-2026-9739?
CVE-2026-9739 affects github.com/googleapis/mcp-toolbox. Use GeekWala's free vulnerability scanner to check your dependencies against CVE-2026-9739 and 200,000+ other known vulnerabilities.

Severity & Exploitability

CVSS Score
9.1

Exploitation is straightforward and causes maximum impact. Patch immediately.

Also Known As

GHSA-7pf3-8xx7-rvhf
GO-2026-5870

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