---
title: "CVE-2026-11720: MCP Toolbox HTTP tool path parameters allow traversal to unintended endpoints"
url: https://erroneo.us/security/cve/CVE-2026-11720/
description: "CVE-2026-11720 (github.com/googleapis/mcp-toolbox (Go)): A path traversal vulnerability exists in the HTTP tool URL builder of googleapis/mcp-toolbox. When…"
type: vulnerability-record
section: "Security Digest"
date_published: 2026-06-29
date_modified: 2026-09-04
publisher: erroneo.us
author: erroneo.us Security Desk
cve: "CVE-2026-11720"
kev: false
cvss: 9.3
epss: 0.00533
license: All rights reserved. Quote with attribution and a link.
---

# CVE-2026-11720: MCP Toolbox HTTP tool path parameters allow traversal to unintended endpoints

**Signal:** Critical and remotely reachable. No known exploitation yet, but it is network-reachable without credentials. (Computed from CISA KEV, EPSS and CVSS; not an editorial verdict.)

## Should you act?

- No confirmed exploitation. It is not in CISA’s KEV catalog and CISA’s SSVC assessment records no known exploitation. That can change quickly after a public write-up; re-check if you are affected.
- EPSS 0.5% , percentile 44: FIRST’s model estimates a 0.5% chance of exploitation activity in the next 30 days, higher than 44% of all scored CVEs (low). EPSS is a probability, not a verdict.
- Remotely reachable with no login and no user interaction. If the vulnerable service is exposed to the internet, prioritize it.
- Only applies if your dependency tree includes github.com/googleapis/mcp-toolbox (Go) < 1.3.0, fixed in 1.3.0 . Check your lockfile, including transitive dependencies.

## What it is

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

- Go `github.com/googleapis/mcp-toolbox` < 1.3.0 → fixed: 1.3.0

## Affected products (CVE record)

- Google MCP Toolbox for Databases (googleapis/mcp-toolbox): < 1.3.0

## Severity

- Google CVSS 4.0: 9.3 `CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N`
- GitHub CVSS 4.0: 9.3 `CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N`

## Exploitation

- CISA KEV: not listed (no confirmed in-the-wild exploitation known to CISA).
- CISA SSVC assessment: exploitation none , automatable yes , technical impact total .
- FIRST EPSS (model of 2026-10-21): 0.53% probability of exploitation activity in the next 30 days; percentile 44.

## Sources

- [GitHub Advisory GHSA-vwxw-jrg6-9jxv](https://github.com/advisories/GHSA-vwxw-jrg6-9jxv)
- [CVE.org record CVE-2026-11720](https://www.cve.org/CVERecord?id=CVE-2026-11720)
- [NVD entry CVE-2026-11720](https://nvd.nist.gov/vuln/detail/CVE-2026-11720)
- [github.com](https://github.com/googleapis/mcp-toolbox/pull/3218)
- [github.com](https://github.com/googleapis/mcp-toolbox/commit/80a66021205e032a424fff87b3dc6d92da58aa77)
- [github.com](https://github.com/googleapis/mcp-toolbox/releases/tag/v1.3.0)

---
Source page: https://erroneo.us/security/cve/CVE-2026-11720/ · Security Digest: https://erroneo.us/security/ · More: https://erroneo.us/llms.txt