Authentication Bypass in Google APIs' MCP Toolbox
CVE-2026-11717

9.3CRITICAL

Key Information:

Vendor

Google
Status
Mcp Toolbox For Databases (googleapis/mcp-toolbox)
Vendor
CVE Published:
18 June 2026

What is CVE-2026-11717?

An authentication bypass vulnerability has been identified in the validation process of opaque tokens within Google APIs' MCP Toolbox. During the token verification via the OAuth 2.0 introspection endpoint, the system fails to reject tokens when the mandatory 'active' key is omitted from the response. This oversight allows potentially unauthorized access to protected tools and data sources, as the condition to verify the token's activity may inadvertently be bypassed. Proper implementation and careful examination of the introspection endpoint responses are crucial to maintain security.

Affected Version(s)

MCP Toolbox for Databases (googleapis/mcp-toolbox) 1.0.0 <= 1.3.0

References

https://github.com/googleapis/mcp-toolbox/pull/3341

CVSS V4

Score:
9.3
Severity:
CRITICAL
Confidentiality:
High
Integrity:
High
Availability:
None
Attack Vector:
Network
Attack Complexity:
Low
Attack Required:
None
Privileges Required:
Undefined
User Interaction:
None

Timeline

  • Vulnerability published

  • Vulnerability Reserved

Credit

HaoNH Leader Redteam From VINCSS ( Member Of Vingroup )
.