CVE-2026-14538: medium-severity vulnerability in Google mcp-toolbox
BigQuery Dataset Allowlist Bypass via Metadata Dry-Run in MCP Toolbox
Published
E-mail alert when it lands in KEV, gets a public PoC or its score goes up.
13Vexday Risk Score
No sign of exploitation. No public exploitation artifact known so far.
ssvc Trackcvss 5.7epss 0.2%
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.
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
Affected products
Google · mcp-toolboxRelated CVEs — Google mcp-toolbox
In the same product, most dangerous first.
CVE-2026-14541HIGHAuthentication Bypass and Audience Confusion in MCP Toolbox OAuth ProviderEPSS 0.3%CVE-2026-14537HIGHAuthorization Bypass in MCP Toolbox Legacy HTTP EndpointsEPSS 0.3%CVE-2026-14539MEDIUMDenial of Service via Unrestricted Payload Buffering in MCP ToolboxEPSS 0.2%CVE-2026-14540HIGHServer-Side Request Forgery via Unrestricted HTTP Redirection in MCP ToolboxEPSS 0.1%