CVE-2026-14538: google mcp_toolbox_for_databases Improper Authorization

Vulnerability summary

CVE-2026-14538 is a high (CVSS 7.7) Improper Authorization vulnerability in google mcp_toolbox_for_databases. EPSS estimates a 0.20% chance of exploitation in the next 30 days, higher than 9.7% of scored vulnerabilities.

Timeline

1. 31-07-2026
   PublishedVulnerability first disclosed.
2. 31-07-2026
   Last modifiedVulnerability information updated.

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.

• CWE-285Improper AuthorizationThe product does not perform or incorrectly performs an authorization check when an actor attempts to access a resource or perform an action.
• CWE-863Incorrect AuthorizationThe product performs an authorization check when an actor attempts to access a resource or perform an action, but it does not correctly perform the check.