CVE-2026-11718Network attack vector

Authentication bypass via omitted introspection issuer

Published Jun 18, 2026 · Updated Jun 18, 2026

Authentication bypass in Google MCP Toolbox for Databases before 1.4.0 allows remote attackers to access protected tools with opaque tokens. The validateOpaqueToken path decodes an introspection response, and validateClaims skips issuer comparison when its optional iss field is empty. Exploitation requires generic opaque-token authentication with a configured issuer and an introspection provider that accepts a token but omits iss, enabling unauthorized access under that token.

CVSS severity9.3
Critical
EPSS probability0.18%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Authentication bypass in Google MCP Toolbox for Databases before 1.4.0 allows remote attackers to access protected tools with opaque tokens. The validateOpaqueToken path decodes an introspection response, and validateClaims skips issuer comparison when its optional iss field is empty. Exploitation requires generic opaque-token authentication with a configured issuer and an introspection provider that accepts a token but omits iss, enabling unauthorized access under that token.

The record

CVE
CVE-2026-11718
Published
Jun 18, 2026
Updated
Jun 18, 2026
Vendor
Go standard library
Product
MCP Toolbox for Databases
Classifications
CWE-287, T1190
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jun 18, 2026CVE publishedPublication date reported by the CVE source.
  2. Jun 18, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=1.0.0 <=1.3.0

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Go standard library · MCP Toolbox for Databasesversion=1.0.0 <=1.3.0

Published CVSS scores

9.3GitHub Advisory DatabaseCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-287Improper Authentication
T1190Exploit Public-Facing Application

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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