Secuno
ENNL
Book demo

CVE-2026-11718

Google Mcp Toolbox For Databases authentication bypass

9.1 CRITICALEPSS 0.18%
  1. Published18 Jun 2026

Description

An authentication bypass vulnerability exists in the generic opaque token validation path (validateOpaqueToken) of googleapis/mcp-toolbox. When the toolbox validates an opaque token via an OAuth 2.0 introspection endpoint (RFC 7662), it decodes the response into an introspectResp struct. However, the subsequent claim-checking logic (validateClaims) evaluates the issuer condition as if a.issuer != "" && iss != "". If the external OAuth provider's introspection response omits the optional iss (issuer) field completely, the variable iss defaults to an empty string. This causes the conditional block to evaluate to false and be skipped silently. Consequently, the application accepts tokens issued by unauthorized or unintended third-party identity providers.

CVSS 3.1 breakdown

Attack vectorNetwork
Attack complexityLow
Privileges requiredNone
User interactionNone
ScopeUnchanged
ConfidentialityHigh
IntegrityHigh
AvailabilityNone
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N

Affected products

Google Mcp Toolbox For Databases≥ 1.0.0 ≤ 1.3.0

Remediation

No fixed version is recorded in the NVD data. Check the vendor advisory for the latest guidance.

References

Related CVEs

Recent high-severity vulnerabilities sharing a weakness type.

CVE-2026-843138.8
Nginx UI is a web user interface for the Nginx web server. Prior to 2.4.1, POST…
CVE-2026-1093728.7
ZITADEL 4.x before 4.19.2 and 3.x through 3.4.15 contains an authentication bypass in…
CVE-2026-1093138.1
Grav Login plugin 2.7.0 before 3.9.9 contains an authentication bypass vulnerability…
CVE-2026-1093128.1
Grav Login plugin 2.7.0 before 3.9.9 contains an authentication bypass in…
CVE-2026-10890710.0
A vulnerability was determined in Netcore NR268 1.7.121109. Affected is the function…
CVE-2026-1088658.2
AmoyLab Unla through 0.10.0 contains an authentication bypass vulnerability that allows…

Frequently asked

Is CVE-2026-11718 being actively exploited?

CVE-2026-11718 is not in the CISA KEV catalog. Its EPSS exploit probability is 0.18%.

How severe is CVE-2026-11718?

CVE-2026-11718 has a CVSS 3.1 base score of 9.1, rated critical. EPSS estimates a 0.18% probability of exploitation.

Which products are affected by CVE-2026-11718?

Affected products include Google Mcp Toolbox For Databases.

How do I fix CVE-2026-11718?

Apply the vendor's patch or advisory guidance, then verify no affected versions remain across your devices.

How Secuno handles this

Secuno correlates vulnerabilities like CVE-2026-11718 against the real software inventory on every managed device, every day. Rather than a static severity, each match is scored in context: exploit availability, EPSS, the asset's exposure, and business criticality decide where it lands in the queue. If an affected version is present anywhere across your portfolio, it surfaces automatically with a prioritised remediation path.

See how prioritisation worksBook a demo

Get Patch this first every Monday

Five vulnerabilities that matter this week, ranked on real exploitation. Plain language, one email, no spam.

You can unsubscribe with one click from every issue. We handle your details as described in our privacy policy.

Data from the NVD, CISA KEV catalog and FIRST EPSS. CVSS 3.1 base score shown where available.