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CVE-2026-11720 — Vulnerability in...

CRITICAL

MCP Toolbox HTTP tool path parameters allow traversal to unintended endpoints

Published June 29, 2026Updated September 10, 2026Source: osv

Summary

A path traversal vulnerability exists in the HTTP tool URL builder of googleapis/mcp-toolbox. When constructing downstream API requests, the URL builder substitutes user-controlled pathParams into the configured tool path and parses the resulting string as a relative URL. While it checks that the input does not alter the scheme, host, or user info, it relies on ResolveReference for the final URL resolution. Because dot segments (../) are normalized during this resolution step, an attacker can supply path parameters containing directory traversal sequences to escape the operator-configured path scope. This allows the client to coerce the toolbox into making requests to unintended endpoints on the same target host while forwarding the toolbox's configured credentials (e.g., bypassing a restricted path like /api/v1/users/{{.id}} to reach /admin/secrets).

Advisory Timeline

  • First published June 29, 2026 (105 days ago).
  • Last revised September 10, 2026 — 73 days after initial publication.

Remediation

Upgrade to the fixed version using your package manager.

Go
Update github.com/googleapis/mcp-toolbox to 1.3.0 or later
go get github.com/googleapis/mcp-toolbox@v1.3.0

After upgrading, run your dependency scanner again to confirm the vulnerability is resolved.

Affected Packages (1)

Affects 1 ecosystem: go (1).

PackageEcosystemAffectedFixed In
github.com/googleapis/mcp-toolbox
go
All versions1.3.0

Vulnerability Classification

Common Weakness Enumeration (CWE) identifiers for this vulnerability type.

CVSS Score Breakdown

What the CVSS (Common Vulnerability Scoring System) 9.1 score means for each attack dimension.

Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
None

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N

References

Frequently Asked Questions

What is CVE-2026-11720?
MCP Toolbox HTTP tool path parameters allow traversal to unintended endpoints This vulnerability has been assigned a severity rating of CRITICAL (CVSS score: 9.1/10).
How do I check if my project is affected by CVE-2026-11720?
CVE-2026-11720 affects github.com/googleapis/mcp-toolbox. Use GeekWala's free vulnerability scanner to check your dependencies against CVE-2026-11720 and 200,000+ other known vulnerabilities.

Severity & Exploitability

CVSS Score
9.1

Exploitation is straightforward and causes maximum impact. Patch immediately.

Also Known As

GHSA-vwxw-jrg6-9jxv
GO-2026-6411

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