CVE-2026-55103

{
  "etk_id": "ETK-2026-1838",
  "cve_id": "CVE-2026-55103",
  "display_id": "CVE-2026-55103",
  "ghsa_id": "GHSA-jw39-rch6-mhwf",
  "euvd_id": "EUVD-2026-102202",
  "status": "published",
  "anchor_state": "anchored",
  "title": "Actor authorization bypass in discourse-activity-pub",
  "summary": "Affected discourse-activity-pub versions do not sufficiently validate the relationship between an inbound ActivityPub request signer, the claimed actor, and the referenced federated post. A remote attacker able to submit signed ActivityPub requests may edit, delete, or reply to federated posts without the expected permissions.",
  "mitigation": "Upgrade discourse-activity-pub to > 3d5d6e7 or later.",
  "vendor": "discourse",
  "product": "discourse-activity-pub",
  "affected": [
    {
      "affected_notes": [],
      "affected_ranges": [
        "<= 3d5d6e7"
      ],
      "ecosystem": null,
      "fixed_versions": [
        "> 3d5d6e7"
      ],
      "package_name": "discourse-activity-pub",
      "purl": null
    }
  ],
  "cwes": [
    345
  ],
  "cvss_score": 8.6,
  "cvss_src": "cna_vendor",
  "cvss_vector": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:N/A:N",
  "epss_score": 0.002,
  "epss_percentile": 0.0928,
  "epss_asof": "2026-10-20",
  "automation": "contextual",
  "check": false,
  "check_confidence_basis": null,
  "exploit": false,
  "pipeline_minutes": 58.06254081666667,
  "t0_at": "2026-10-15T17:05:41.414000+00:00",
  "signals": {
    "trigger_signal": {
      "at": "2026-10-15T17:05:41.414000+00:00",
      "days": 0,
      "is_lower_bound": false,
      "measured_at": "2026-10-15T17:05:41.414000+00:00",
      "url": "https://www.cve.org/CVERecord?id=CVE-2026-55103"
    }
  }
}