ETK-2026-921Zero's internal tracking ID, independent of the CVE number.

{
  "etk_id": "ETK-2026-921",
  "cve_id": null,
  "display_id": "ETK-2026-921",
  "ghsa_id": "GHSA-g7gq-2r4g-3qw8",
  "euvd_id": null,
  "status": "published",
  "anchor_state": "awaiting_cve",
  "title": "MCP policy middleware bypass in ToolHive",
  "summary": "ToolHive versions 0.13.0 through 0.51.3 can allow MCP requests to bypass configured validation, mutation, and rate-limit middleware. A client able to reach the proxy and satisfy any enabled authentication may evade those controls when Cedar authorization is not enabled.",
  "mitigation": "Upgrade github.com/stacklok/toolhive to version 0.51.4 or later. Until upgrading, enable Cedar authorization to reject requests that do not pass MCP parsing.",
  "vendor": "go",
  "product": "go:github.com/stacklok/toolhive",
  "affected": [
    {
      "affected_notes": [],
      "affected_ranges": [
        ">= 0.13.0, < 0.51.4"
      ],
      "ecosystem": "go",
      "fixed_versions": [
        "0.51.4"
      ],
      "package_name": "github.com/stacklok/toolhive",
      "purl": "pkg:golang/github.com/stacklok/toolhive"
    }
  ],
  "cwes": [
    436
  ],
  "cvss_score": 7.1,
  "cvss_src": "cna_vendor",
  "cvss_vector": "CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:L",
  "epss_score": null,
  "epss_percentile": null,
  "epss_asof": null,
  "automation": "contextual",
  "check": false,
  "check_confidence_basis": null,
  "exploit": false,
  "pipeline_minutes": 34.54850205,
  "t0_at": null,
  "signals": {
    "public_poc": {
      "at": "2026-10-07T11:31:59+00:00",
      "days": -14.46253090326389,
      "is_lower_bound": true,
      "measured_at": "2026-10-21T22:38:01.708154+00:00",
      "url": "https://github.com/stacklok/toolhive/security/advisories/GHSA-g7gq-2r4g-3qw8"
    },
    "trigger_signal": {
      "at": "2026-10-07T11:31:59+00:00",
      "days": -14.46253090326389,
      "is_lower_bound": true,
      "measured_at": "2026-10-21T22:38:01.708154+00:00",
      "url": "https://github.com/stacklok/toolhive/security/advisories/GHSA-g7gq-2r4g-3qw8"
    }
  }
}