CVE-2026-11720: Google MCP Toolbox path traversal in HTTP tool URL builder

CVE-2026-11720 · Severity: critical · CVSS 9.1 · Published 2026-06-29

The MCP Toolbox's HTTP tool allows an attacker to bypass configured API path restrictions by injecting directory traversal sequences into URL parameters. This enables unauthorized access to sensitive endpoints (such as admin or secrets pages) on the same server while reusing the toolbox's configured credentials. The vulnerability affects any deployment using the HTTP tool without additional input validation.

Technologies: github.com/googleapis/mcp-toolbox (Go), Google MCP Toolbox, Google MCP Toolbox for Databases. Vendors: Go, Google.

Quick answers

Is CVE-2026-11720 exploited in the wild?
No. Junglewise Threat Intelligence has no report of CVE-2026-11720 being exploited in the wild.
How severe is CVE-2026-11720?
Critical severity, with a CVSS score of 9.1, published 29 June 2026.
Which products and versions are affected?
github.com/googleapis/mcp-toolbox (Go) < 1.3.0, SEMVER:introduced=0,fixed=1.3.0; Google MCP Toolbox < 1.3.0; Google MCP Toolbox for Databases < 1.3.0.
Is there a fix for CVE-2026-11720?
Yes. github.com/googleapis/mcp-toolbox (Go): upgrade to 1.3.0 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
How is CVE-2026-11720 attacked?
It is attacked over the network, in a software library.
Am I affected by CVE-2026-11720?
Check whether you run github.com/googleapis/mcp-toolbox (Go), Google MCP Toolbox or Google MCP Toolbox for Databases at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

How to fix

  • github.com/googleapis/mcp-toolbox (Go): upgrade to 1.3.0 or later
    go get github.com/googleapis/mcp-toolbox@v1.3.0

Technical details

The vulnerability is a path traversal flaw (CWE-22) in the HTTP tool's URL builder component. The root cause is the use of Go's ResolveReference() function, which normalizes dot segments (..) during URL resolution. An unauthenticated network attacker can inject URL-encoded or literal dot-segment sequences (e.g., ../, %2e%2e) into path parameters to escape the operator-configured base path. For example, a tool restricted to /api/v1/users/{{.id}} can be coerced to request /admin/secrets by supplying a crafted id parameter. The attacker needs network access to invoke the HTTP tool but requires no authentication or user interaction. The fix, released in version 1.3.0, rejects relative and encoded dot segments and validates that resolved paths remain within the intended base path scope, supplemented by pathEscape and queryEscape template functions for safe parameter substitution.

Affected products

  • Google MCP Toolbox < 1.3.0

Identifiers

  • CVE-2026-11720
  • GHSA-vwxw-jrg6-9jxv
  • GO-2026-6411

Timeline

  • 2026-06-29: disclosed: Published to GitHub Advisory Database
  • 2026-05-21: patched: Fixed in version 1.3.0 released
  • 2026-09-04: advisory: GitHub security review completed

References

This page as Markdown. Free to reuse under CC BY 4.0 with a link back.