---
id: CVE-2026-11720
aliases:
  - GHSA-vwxw-jrg6-9jxv
title: MCP Toolbox HTTP tool path parameters allow traversal to unintended endpoints
summary: MCP Toolbox HTTP tool path parameters allow traversal to unintended endpoints
severity: critical
cvss: 9.1
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N'
vendor: googleapis
product: github.com/googleapis/mcp-toolbox
ecosystem: go
affected:
  - github.com/googleapis/mcp-toolbox < 1.3.0
patched:
  - github.com/googleapis/mcp-toolbox 1.3.0
published: '2026-06-29'
updated: '2026-09-04'
source: OSV
sourceUrl: 'https://osv.dev/vulnerability/GHSA-vwxw-jrg6-9jxv'
references:
  - url: 'https://nvd.nist.gov/vuln/detail/CVE-2026-11720'
  - url: 'https://github.com/googleapis/mcp-toolbox/pull/3218'
  - url: >-
      https://github.com/googleapis/mcp-toolbox/commit/80a66021205e032a424fff87b3dc6d92da58aa77
  - url: 'https://github.com/googleapis/mcp-toolbox'
  - url: 'https://github.com/googleapis/mcp-toolbox/releases/tag/v1.3.0'
tags:
  - osv
  - go
epss: 0.00533
epssPercentile: 0.42611
ingestedAt: '2026-09-05T19:33:48.345Z'
---

## Overview

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).

## Affected packages

- `github.com/googleapis/mcp-toolbox < 1.3.0`

## Remediation

Upgrade to a patched release:

- `github.com/googleapis/mcp-toolbox 1.3.0`