High Access control

CVE-2026-14538 — BigQuery Dataset Allowlist Bypass via Metadata Dry-Run in MCP Toolbox

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.

Published Jul 30, 2026 · Updated Oct 15, 2026 · Sources: NIST National Vulnerability Database, CVE Program (cve.org) e CISA ADP · CNA: Google

Low

Who exploits it and how urgent it is

A 0–100 score combining confirmed exploitation, ransomware and APT use, public exploits, EPSS and severity.

No exploitation signal in the sources consulted so far.

How the score was calculated

Technical severity (high)+6

The score orders the patch queue; it does not replace your asset context (internet exposure, criticality, compensating controls).

Triage

Is it exploited, how likely is exploitation, what does it touch, and how severe do the sources call it.

Exploitation

Not confirmed

Not in CISA KEV — an absence of record, not proof it is unexploited.

EPSS FIRST

—

No EPSS score.

Affects

Google

Mcp Toolbox For Databases and 1 more

CVSS base

7.7

High · 3 source(s)

CISA SSVC assessment CISA

Three decision points CISA publishes for the CVEs it assesses (SSVC 2.0.3). A stakeholder decision, not a severity score.

Exploitation

None

none · proof-of-concept · active

Automatable

can an attacker script the kill-chain steps

Technical impact

Partial

partial · total control of the vulnerable component

Remediation

Fixes and mitigations documented by the sources — linked to the original advisory.

Documented patch — github.com (NIST National Vulnerability Database)

First 24 hours

Ordered from the record’s own fields — exposure first, because you cannot patch what you have not found. A rule-generated starting point.

Identify exposed assets running the affected vendor/product/version combinations (Google Mcp Toolbox For Databases, Google Mcp-toolbox).
Apply the fixed version or the patch documented under Remediation.
Search available logs for exploit probes matching the vulnerability class (access control), errors and authentication anomalies.

Affected scope

Vendor, product and versions as the sources word them.

Vendor	Product	Versions	Status	Source
Google	Mcp Toolbox For Databases	≥ 0.16.1 and ≤ 1.4.0	Vulnerable	NIST National Vulnerability Database
Google	Mcp-toolbox	≥ 0.16.1 and ≤ 1.4.0	Vulnerable	CVE Program (cve.org) e CISA ADP

Attack characteristics

The CVSS vector, decoded. It describes the attack, not your exposure to it.

Attack vector

Network

Attack complexity

Low

Privileges required

Low

User interaction

None

Scope

Changed

Confidentiality

High

Integrity

None

Availability

None

Every base score collected

Sources score independently and may disagree; each row says who scored it and under which version.

Score	Version	Severity	Expl.	Impact	Scored by
5.7	CVSS 4.0	Medium	—	—	cve-coordination@google.com via NIST National Vulnerability Database
5.7	CVSS 4.0	Medium	—	—	Google via CVE Program (cve.org) e CISA ADP
7.7	CVSS 3.1	High	3.1	4.0	nvd@nist.gov via NIST National Vulnerability Database

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:N/A:N (score shown at the top: nvd@nist.gov)

Weakness MITRE

Weakness class according to MITRE’s CWE catalog.

CWE-285 · Improper Authorization

Other CVEs with this weakness →

Detection

Read off the CVSS vector and the weakness class. Starting points, not tested rules.

Prioritize edge telemetry for the network-reachable component (proxy, WAF, IDS/IPS).
Audit administrative actions and access to resources outside each user’s normal pattern.

web/proxy/WAF logsnetwork IDS/IPSauthentication logsapplication logs

Timeline

What happened to this CVE, newest first.

2026
Affected products added · google/mcp-toolbox
Oct 15, 2026 · CVE Program (cve.org) e CISA ADP
SSVC assessment updated
Oct 15, 2026 · CVE Program (cve.org) e CISA ADP
Record published
Oct 15, 2026
Fix documented
Oct 15, 2026 · NIST National Vulnerability Database
CVSS changed · 7.7
Oct 15, 2026 · NIST National Vulnerability Database
Source status changed · → Analyzed
Oct 15, 2026 · NIST National Vulnerability Database
Record created in this database
Oct 15, 2026 · NIST National Vulnerability Database
CVE published
Jul 30, 2026 · Google

Source activity

Repeated readings are counted rather than listed.

1× Official description updated · Oct 15, 2026 – Oct 15, 2026

References

1 on the record

github.com/googleapis/mcp-toolbox/pull/3452
Issue Tracking, Patch, NIST National Vulnerability Database

Elsewhere on this site

Google
every CVE for this vendor

Access control
same class

CWE-285
other pages naming this weakness

Related CVEs (same products)

High CVE-2026-14541 Authentication Bypass and Audience Confusion in MCP Toolbox OAuth Provider Jul 31, 2026
Medium CVE-2026-14540 Server-Side Request Forgery via Unrestricted HTTP Redirection in MCP Toolbox Jul 30, 2026
High CVE-2026-14539 Denial of Service via Unrestricted Payload Buffering in MCP Toolbox Jul 30, 2026
Critical CVE-2026-14537 Authorization Bypass in MCP Toolbox Legacy HTTP Endpoints Jul 30, 2026
High CVE-2026-16481 Server-Side Request Forgery (SSRF) and Credential Exfiltration in googleapis/mcp-toolbox cloud-healthcare-fhir-fetch-page Tool Jul 27, 2026
High CVE-2026-15829 SQL Injection and Security Boundary Bypass in googleapis/mcp-toolbox Jul 21, 2026

Not in any source we poll

Listed rather than left blank: an empty field and an unmeasured one look identical on screen, and only one is a reason to look elsewhere.

No FIRST EPSS score.
No confirmed IOCs, IP addresses, domains, file hashes, or malware artifacts supplied.
No organization-specific asset inventory, compensating-control status, or patch deployment evidence supplied.
No exploit packet captures, log samples, or incident case IDs supplied.

Answered from this record

Text assembled only from the fields above — no additional claims.

What should defenders know first?

CVE-2026-14538 is "BigQuery Dataset Allowlist Bypass via Metadata Dry-Run in MCP Toolbox", rated High. It affects Mcp Toolbox For Databases (Google); versions are in the scope table. It is not in CISA KEV, which does not rule out exploitation. CVSS 7.7 describes technical severity. First verify whether exposed or business-critical assets run the affected versions, apply vendor fixes or mitigations, and preserve logs for review.

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