CVE-2026-14538 BigQuery Dataset Allowlist Bypass via Metadata Dry-Run in MCP Toolbox
Authenticated attackers can bypass dataset allowlists in Google MCP Toolbox to read unauthorized schemas and federated data.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- None listed
What is CVE-2026-14538?
CVE-2026-14538 is a medium-severity missing authorization vulnerability in Google mcp-toolbox, published on 31 Jul 2026. Any signed-in user can exploit it over the network, with no action from the victim.
Official 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.
Which versions are affected by CVE-2026-14538?
It affects 1 product.
Products include Google Mcp Toolbox for Databases.
How do I fix CVE-2026-14538?
No fix has been published for CVE-2026-14538 yet. Limit exposure of the affected software until one is available.
Upgrade, and check permissions on every request on the server, not only in the interface. More about Missing authorization.
Is CVE-2026-14538 being exploited?
There is no known exploitation of CVE-2026-14538 in the wild and no public exploit code.
Other vulnerabilities in Google mcp-toolbox
- CVE-2026-11720 Path Traversal in googleapis/mcp-toolbox HTTP Tool URL Builder
- CVE-2026-11717 googleapis/mcp-toolbox: authentication bypass vulnerability in the generic opaque token validation path (validateOpaqueToken)
- CVE-2026-11718 googleapis/mcp-toolbox: authentication bypass vulnerability in the generic opaque token validation path (validateOpaqueToken)
- CVE-2026-15829 SQL Injection and Security Boundary Bypass in googleapis/mcp-toolbox
- CVE-2026-11719 MCP Toolbox for Databases: authenticated authorization bypass
Sources
Also known as GHSA-24pp-m59v-92j8.