CVE-2026-11718: An authentication bypass vulnerability exists in the generic opaque token validation path (validateOpaqueToken

This month

CRITICAL 9.1REMOTEUPGRADE

CVE-2026-11718 is a critical-severity flaw (CVSS 9.1) affecting mcp toolbox for databases. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

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

Why this priority

Critical severity
Remotely exploitable, no login, no user action

A fixed release or distro patch exists.

Risk facts

CVSS score	9.1 (Critical)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	0.2% (top 92%)
CISA exploited list	No
Weakness	CWE-287
Published	2026-06-18
Last modified	2026-10-26

Publisher (CNA): Google Inc. · Vendor: google

Last updated 2026-10-26 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-06-18 14:17 UTCPublished CVE record published
2026-10-26 11:10 UTCUpdated Record last modified

google mcp toolbox for databases UPGRADE

Affected: >= 1.0.0 and <= 1.3.0

Fixed in: newer than 1.3.0

Safe to downgrade to: a release before 1.0.0

1. Check installed version

apt-cache policy mcp-toolbox-for-databases || rpm -q mcp-toolbox-for-databases || mcp-toolbox-for-databases --version

2. UPGRADE to newer than 1.3.0 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade mcp-toolbox-for-databases

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade mcp-toolbox-for-databases

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

3. If no update is available yet, DOWNGRADE to a release before 1.0.0 (Debian / Ubuntu)

apt-cache madison mcp-toolbox-for-databases sudo apt install mcp-toolbox-for-databases=<VERSION_BEFORE_1.0.0> sudo apt-mark hold mcp-toolbox-for-databases

3. If no update is available yet, DOWNGRADE (RHEL / Amazon Linux / Fedora)

dnf --showduplicates list mcp-toolbox-for-databases sudo dnf downgrade mcp-toolbox-for-databases-<VERSION_BEFORE_1.0.0> sudo dnf versionlock add mcp-toolbox-for-databases

Downgrade risk

Downgrading can break dependent software and may reopen older bugs. Read the distro advisory first and test on a non-production host.

After downgrade

Restart the service, and keep the package held until a fixed release ships.

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2026-11718?

mcp toolbox for databases: upgrade to newer than 1.3.0. Exact commands for each OS are on this page.

Is CVE-2026-11718 being exploited?

CVE-2026-11718 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2026-11718 affect?

CVE-2026-11718 affects mcp toolbox for databases. Severity is critical (CVSS 9.1). 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 de

How urgent is CVE-2026-11718?

Priority 39/100. Critical severity; Remotely exploitable, no login, no user action

Related CVEs

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References

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