CVE-2026-11718

Published: Jun 18, 2026Updated: Aug 17, 2026 Sources: CVE List NVDCWE-287

9.1CRITICAL

NVD MITRE

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.

No summary for this CVE yet.

CVSS Vector Breakdown

Exploitability

AV:NAttack Vector

Network

AC:LAttack Complexity

Low

PR:NPrivileges Required

None

UI:NUser Interaction

None

Scope

S:UScope

Unchanged

Impact

C:HConfidentiality

High

I:HIntegrity

High

A:NAvailability

None

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Weaknesses

CWE-287

Affected Products

Google

commercial·USaka google inc, google llc

mcp toolbox for databasesOn-premDatabase

Databases / db-tooling

MCP Toolbox for Databases (googleapis/mcp-toolbox)On-premDesktop App

Databases / db-tooling

Exploitability

Official Patch Available

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Attack Graph

Products CVE Techniques Tactics

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MITRE ATT&CK

2 techniques

Initial Access

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References

https://github.com/googleapis/mcp-toolbox/pull/3360

github.com

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