CVE-2026-44550: Open webui Open WebUI's Mass Assignment Vulnerability

{
  "schema_version" : "1.4.0",
  "id" : "GHSA-hr43-rjmr-7wmm",
  "modified" : "2026-05-15T23:52:16Z",
  "published" : "2026-05-08T19:38:54Z",
  "aliases" : [ "CVE-2026-44550" ],
  "summary" : "Open WebUI's Mass Assignment via Pydantic extra='allow' Allows Creating Folders in Other Users' Accounts",
  "details" : "# Mass Assignment via Pydantic extra='allow' Allows Creating Folders in Other Users' Accounts\n\n## Affected Component\n\nFolder creation endpoint and form model:\n- `backend/open_webui/models/folders.py` (lines 72-77, `FolderForm` with `extra='allow'`)\n- `backend/open_webui/models/folders.py` (lines 95-106, `insert_new_folder` dict construction)\n- `backend/open_webui/routers/folders.py` (line 119, `create_folder` endpoint)\n\n## Affected Versions\n\nCurrent main branch (commit `6fdd19bf1`) and likely all versions since `FolderForm` adopted `extra='allow'`.\n\n## Description\n\n`FolderForm` uses `model_config = ConfigDict(extra='allow')`, which permits arbitrary fields to pass through Pydantic validation and be included in `model_dump(exclude_unset=True)`. In `insert_new_folder`, the server-assigned `user_id` is placed at the start of the dict and then overwritten by the spread of form data:\n\n```python\n# models/folders.py:95-106\nfolder = FolderModel(\n    **{\n        'id': id,                                              # server\n        'user_id': user_id,                                    # server — overwritten below\n        **(form_data.model_dump(exclude_unset=True) or {}),    # user-controlled (extra='allow')\n        'parent_id': parent_id,\n        'created_at': int(time.time()),\n        'updated_at': int(time.time()),\n    }\n)\n```\n\nBecause `FolderModel` declares `user_id: str` as a real field (not just a form extra), any attacker-supplied `user_id` in the POST body is accepted by the model and persisted on the `Folder` row.\n\n## Attack Scenario\n\n1. Attacker discovers a victim's user ID. User UUIDs commonly leak via the user search endpoint (`GET /api/v1/users/search`, intentionally accessible to verified users for sharing UI), shared chat metadata, or channel member lists.\n2. Attacker sends:\n   ```\n   POST /api/v1/folders/\n   {\n     \"name\": \"Important: Click here\",\n     \"user_id\": \"<victim_user_id>\",\n     \"meta\": {\"icon\": \"warning\"},\n     \"data\": {...}\n   }\n   ```\n3. Pydantic accepts the extra `user_id` field (allowed by `extra='allow'`).\n4. `insert_new_folder` spreads the form data over the server-set `'user_id': user_id`, overwriting it with the attacker's value.\n5. The `Folder` row is persisted with `user_id = <victim_user_id>`.\n6. The victim sees the attacker-planted folder in their UI on next load because `GET /api/v1/folders/` filters by the viewer's own `user_id`.\n\nThe attacker can repeat this to plant multiple folders, use crafted `name` values for phishing (\"Click here to recover account\" / \"Security alert\"), and abuse the `meta` and `data` fields to add visual elements that further mimic legitimate content.\n\n## Impact\n\n- Unauthorized write into victim's folder tree\n- Phishing surface: attacker-controlled `name`, `meta`, and `data` render in the victim's UI in a trusted context\n- DoS / spam: attacker can flood a victim with arbitrary folders; victim must manually delete each one\n- Attacker cannot read the folder back — all read paths filter by the caller's own `user_id` — so confidentiality is preserved, but integrity and trust are compromised\n\n## Preconditions\n\n- Attacker must have an authenticated account with `features.folders` permission (default for all users)\n- Attacker must know or guess the victim's user UUID (obtainable through various non-sensitive endpoints)",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:N/I:L/A:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "PyPI",
      "name" : "open-webui"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "0.9.0"
      } ]
    } ],
    "database_specific" : {
      "last_known_affected_version_range" : "<= 0.8.12"
    }
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/open-webui/open-webui/security/advisories/GHSA-hr43-rjmr-7wmm"
  }, {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-44550"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/open-webui/open-webui"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-862" ],
    "severity" : "MODERATE",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-05-08T19:38:54Z",
    "nvd_published_at" : "2026-05-15T20:16:46Z"
  }
}