CVE-2026-14538

BigQuery Dataset Allowlist Bypass via Metadata Dry-Run in MCP Toolbox

Published Jul 31, 2026 CVSS 4.0 · 5.7 Medium EPSS < 1% KEV · Not listed
Description
An improper authorization and security-boundary bypass vulnerability in the bigquery-execute-sql tool component of Google mcp-toolbox versions 0.16.1 through 1.4.0 allows an authenticated attacker to bypass allowedDatasets validation checks. The toolbox relies on the BigQuery dry-run API to enforce dataset restrictions, but due to a fail-open logic flaw, it bypasses validation when the API returns an empty array for specialized constructs. This allows the attacker to extract structural DDL schemas for explicitly excluded datasets via INFORMATION_SCHEMA, and access downstream federated row data via EXTERNAL_QUERY connections.

Remediation

No solution or workaround provided in the CVE record

Tracking

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Advisories

No advisories available
History
Type Values Removed Values Added
First Time appeared Google
Google mcp-toolbox
Vendors & Products Google
Google mcp-toolbox
Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}

Type Values Removed Values Added
Description An improper authorization and security-boundary bypass vulnerability in the bigquery-execute-sql tool component of Google mcp-toolbox versions 0.16.1 through 1.4.0 allows an authenticated attacker to bypass allowedDatasets validation checks. The toolbox relies on the BigQuery dry-run API to enforce dataset restrictions, but due to a fail-open logic flaw, it bypasses validation when the API returns an empty array for specialized constructs. This allows the attacker to extract structural DDL schemas for explicitly excluded datasets via INFORMATION_SCHEMA, and access downstream federated row data via EXTERNAL_QUERY connections.
Title BigQuery Dataset Allowlist Bypass via Metadata Dry-Run in MCP Toolbox
Weaknesses CWE-285
CWE-863
References
Metrics cvssV4_0

{'score': 5.7, 'vector': 'CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:H/VI:N/VA:N/SC:H/SI:N/SA:N/E:U'}

Weaknesses

Sources

Status
PUBLISHED
Assigner
Google
Published
Updated
Jul 31, 2026, 4:09 PM
Reserved
Jul 3, 2026, 2:06 AM
Status
Analyzed
Published
Jul 31, 2026, 2:16 AM
Modified
Oct 23, 2026, 11:10 PM