Improper Authorization and Security-Boundary Bypass in Google BigQuery Component
CVE-2026-14538

5.7MEDIUM

Key Information:

Vendor

Google
Status
Mcp-toolbox
Vendor
CVE Published:
31 July 2026

What is CVE-2026-14538?

An improper authorization and security-boundary bypass vulnerability exists in the bigquery-execute-sql tool of Google mcp-toolbox versions 0.16.1 through 1.4.0. This flaw permits authenticated attackers to circumvent validation checks performed by allowedDatasets due to a fail-open logic error in the toolbox. When using the BigQuery dry-run API, if an empty array is returned, the toolbox fails to enforce dataset restrictions. As a result, attackers can exploit this weakness to access structural DDL schemas for datasets that should be explicitly excluded and retrieve downstream data through EXTERNAL_QUERY connections.

Affected Version(s)

mcp-toolbox 0.16.1 <= 1.4.0

References

https://github.com/googleapis/mcp-toolbox/pull/3452

CVSS V4

Score:
5.7
Severity:
MEDIUM
Confidentiality:
High
Integrity:
None
Availability:
None
Attack Vector:
Network
Attack Complexity:
Low
Attack Required:
None
Privileges Required:
Undefined
User Interaction:
None

Timeline

  • Vulnerability published

  • Vulnerability Reserved

Credit

HE WEI (ギカク)
.