ETK-2026-2560Zero's internal tracking ID, independent of the CVE number.

{
  "etk_id": "ETK-2026-2560",
  "cve_id": null,
  "display_id": "ETK-2026-2560",
  "ghsa_id": "GHSA-67m7-gf4w-hw23",
  "euvd_id": null,
  "status": "published",
  "anchor_state": "awaiting_cve",
  "title": "TLS 1.3 upstream hostname verification bypass in H2O",
  "summary": "H2O reverse proxies using TLS 1.3 may accept an HTTPS upstream certificate without confirming that its name matches the configured upstream. A network-positioned attacker with a certificate trusted for a different hostname could impersonate that upstream and inspect or modify proxied traffic. The issue applies when `proxy.ssl.verify-peer: ON` is enabled and TLS 1.3 is negotiated.",
  "mitigation": "Upgrade h2o to commits ae55300 and above or later.",
  "vendor": "other",
  "product": "other:h2o",
  "affected": [
    {
      "affected_notes": [
        "commits up to d90ff82"
      ],
      "affected_ranges": [],
      "ecosystem": "other",
      "fixed_versions": [
        "commits ae55300 and above"
      ],
      "package_name": "h2o",
      "purl": null
    }
  ],
  "cwes": null,
  "cvss_score": 7.4,
  "cvss_src": "cna_vendor",
  "cvss_vector": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N",
  "epss_score": null,
  "epss_percentile": null,
  "epss_asof": null,
  "automation": "contextual",
  "check": false,
  "check_confidence_basis": null,
  "exploit": false,
  "pipeline_minutes": 12.704363683333334,
  "t0_at": null,
  "signals": {
    "trigger_signal": {
      "at": "2026-10-23T08:48:26+00:00",
      "days": -1.6019774476041666,
      "is_lower_bound": true,
      "measured_at": "2026-10-24T23:15:16.890846+00:00",
      "url": "https://github.com/h2o/h2o/security/advisories/GHSA-67m7-gf4w-hw23"
    }
  }
}