CVE-2026-16453

{
  "etk_id": "ETK-2026-1767",
  "cve_id": "CVE-2026-16453",
  "display_id": "CVE-2026-16453",
  "ghsa_id": "GHSA-x9f3-cqmx-7phq",
  "euvd_id": "EUVD-2026-102745",
  "status": "published",
  "anchor_state": "anchored",
  "title": "SAML RelayState integrity flaw in Mattermost",
  "summary": "Mattermost 11.7.9 and earlier 11.7.x releases, 11.8.5 and earlier 11.8.x releases, 11.9.1 and earlier 11.9.x releases, and 11.10.0 are affected. An authenticated SAML user may join teams, including invite-only teams, without valid authorization by altering RelayState data. SAML authentication is required.",
  "mitigation": "Upgrade Mattermost to a vendor release that is newer than the affected release in your supported version line. Until upgraded, restrict SAML access to trusted users and review team membership for unauthorized additions.",
  "vendor": "Mattermost",
  "product": "Mattermost",
  "affected": [
    {
      "affected_notes": [],
      "affected_ranges": [
        ">= 11.10.0, <= 11.10.0",
        ">= 11.7.0, <= 11.7.9",
        ">= 11.9.0, <= 11.9.1",
        ">= 11.8.0, <= 11.8.5"
      ],
      "ecosystem": null,
      "fixed_versions": [],
      "package_name": "Mattermost",
      "purl": null
    }
  ],
  "cwes": [
    472
  ],
  "cvss_score": 7.1,
  "cvss_src": "cna_vendor",
  "cvss_vector": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:L/A:N",
  "epss_score": 0.0019,
  "epss_percentile": 0.0777,
  "epss_asof": "2026-10-20",
  "automation": "deterministic",
  "check": true,
  "check_confidence_basis": "differential",
  "exploit": false,
  "pipeline_minutes": 32.53108653333334,
  "t0_at": "2026-10-16T07:08:48.627000+00:00",
  "signals": {
    "check": {
      "at": "2026-10-16T11:24:30.573491+00:00",
      "days": 0.1775688251273148,
      "is_lower_bound": false,
      "measured_at": "2026-10-16T07:08:48.627000+00:00",
      "url": null
    },
    "trigger_signal": {
      "at": "2026-10-16T07:08:48.627000+00:00",
      "days": 0,
      "is_lower_bound": false,
      "measured_at": "2026-10-16T07:08:48.627000+00:00",
      "url": "https://www.cve.org/CVERecord?id=CVE-2026-16453"
    }
  }
}