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Critical, CVSS 9.3amended

MCP Toolbox HTTP tool path parameters allow traversal to unintended endpoints

CVE-2026-11720GHSA-vwxw-jrg6-9jxv

What to do

Vendor fix available. Upgrade each affected package to the fixed version on its release line (github.com/googleapis/mcp-toolbox 1.3.0), redeploy, then verify what is actually installed.

This page has no inventory attached, so it cannot say whether you are affected. A vendor fix is not proof that your deployment is fixed.

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Affected packages

Sources

Severity and exploitation
Exploitation
No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.
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 · score source
EPSS
  • CVE-2026-11720: 0.53% estimated exploitation activity in the next 30 days; percentile 45.08 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.
Source description

As published by the source; long descriptions are shortened.

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).

Dates and revisions
Published by the source
Last modified by the source
Source last checked
  1. Revision 3 · amended ·

    Amended from ghsa record GHSA-vwxw-jrg6-9jxv

  2. Revision 2 · amended ·

    Reviewed OSV alias/range/CVSS4 correction; package source scopes and original publication preserved. No customer finding resolved.

  3. Revision 1 · created ·

    Published from osv record GO-2026-6411

Agent brief

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# Patch Next advisory brief: CVE-2026-11720

Advisory: MCP Toolbox HTTP tool path parameters allow traversal to unintended endpoints
IDs: CVE-2026-11720, GHSA-vwxw-jrg6-9jxv
Record: https://patchnext.com/advisories/cve-2026-11720 (revision 3, source checked 26 Oct 2026, 15:29 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Critical (CVSS 9.3)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: github.com/googleapis/mcp-toolbox 1.3.0. A vendor fix does not mean a deployment is fixed.

## Affected components
- Go github.com/googleapis/mcp-toolbox: affected < 1.3.0; fixed in 1.3.0

## Suggested inspection (read-only)
- Go github.com/googleapis/mcp-toolbox: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on github.com/googleapis/mcp-toolbox.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://osv.dev/vulnerability/GO-2026-6411 (OSV record GO-2026-6411 lists affected ranges: Go github.com/googleapis/mcp-toolbox >=0 <1.3.0 (fixed))
- Verified: https://github.com/advisories/GHSA-vwxw-jrg6-9jxv (GitHub-reviewed advisory GHSA-vwxw-jrg6-9jxv lists affected ranges: Go github.com/googleapis/mcp-toolbox >=0 <1.3.0)

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