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TI-2026-12271 Aliases CVE-2026-14541GHSA-656w-qf75-c5gf

Authentication Bypass and Audience Confusion in MCP Toolbox OAuth Provider

Priority MEDIUM 42CWE-287Published · Updated

Key facts

Attack vector
Network
Privileges required
None
User interaction
None
Attack complexity
Low
Attack requirements
None
Impact type
Security bypass
Confidentiality · integrity · availability
High · High · None
Fix status
No fix listed

Attack profile from CVSS 4.0 · CNA. Fix status from CNA. Impact type from CWE-287.

Summary

An authentication bypass and audience confusion vulnerability exists in the Google OAuth provider component of Google mcp-toolbox version 1.4.0. When a Google authService is initialized with mcpEnabled: true but lacks an explicitly defined audience or clientId, the ValidateMCPAuth pipeline for opaque tokens skips audience validation entirely. As a result, the toolbox will accept any valid Google OAuth access token—even those minted for unrelated ecosystem applications—granting unauthorized clients access to protected tools and data backends.

Why it matters now

Exploitation None reported CISA SSVC · not in CISA KEV
EPSS 0.00253 16th percentileScored 2026-11-07
Fix No fix listed No fixed version in the sources yet

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation
None
Automatable
Yes
Technical impact
Total

The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.

Affected products

VendorProductAffected versionsFixed inStatusSource
Googlemcp-toolbox1.4.0—No fix listedCNA
  • mcp-toolbox VendorGoogle Affected 1.4.0 Fixed in — No fix listed CNA

CPE configurations NVD · 1

CPEVersionsRoleVendor
cpe:2.3:a:google:mcp_toolbox_for_databases:1.4.0:*:*:*:*:*:*:*1.4.0VulnerableGoogle
  • cpe:2.3:a:google:mcp_toolbox_for_databases:1.4.0:*:*:*:*:*:*:* Versions 1.4.0 Vulnerable ·Google

Remediation

No fixed version listed by the sources yet.

Timeline

  1. 2026-10-02 Threatist record created from CVE-2026-14541
  2. 2026-10-03 Alias added: GHSA-656w-qf75-c5gf

References

Patch 1

  • TI-2026-10124 Path Traversal in googleapis/mcp-toolbox HTTP Tool URL Builder CVSS 4.0CRITICAL 9.3
  • TI-2026-10122 Improper authentication in Google MCP Toolbox for Databases CVSS 4.0CRITICAL 9.3
  • TI-2026-10121 Improper authentication in Google MCP Toolbox for Databases CVSS 4.0CRITICAL 9.3
  • TI-2026-12267 Authorization Bypass in MCP Toolbox Legacy HTTP Endpoints CVSS 4.0HIGH 8.1
  • TI-2026-12270 Server-Side Request Forgery via Unrestricted HTTP Redirection in MCP Toolbox CVSS 4.0HIGH 8.0
  • TI-2026-13310 SQL Injection and Security Boundary Bypass in googleapis/mcp-toolbox CVSS 4.0HIGH 8.6
See all 10 →

Sources

This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences