CVE-2026-54009: Open WebUI Cross-user File Disclosure Vulnerability

{
  "schema_version" : "1.4.0",
  "id" : "GHSA-wch8-mhj5-9frg",
  "modified" : "2026-07-20T21:03:45Z",
  "published" : "2026-06-17T14:11:44Z",
  "aliases" : [ "CVE-2026-54009" ],
  "summary" : "Open WebUI: Cross-user file disclosure via /api/chat/completions image_url field",
  "details" : "## summary\n\n`POST /api/chat/completions` accepts an `image_url.url` value that, when it does NOT start with `http://`, `https://`, or `data:image/`, is interpreted as a file id and resolved against the global file table with no ownership check. An authenticated user can therefore set `image_url.url` to another user's file id, the server reads that file from disk, base64-encodes it, and injects the data URI into the LLM request. The user then prompts the LLM to describe / OCR the file and reads the content back.\n\nSame class as CVE-2026-44560 (RAG cross-user access) and the multiple `has_access_to_file` checks added in `routers/files.py` -- the auth boundary was tightened on the file router but not on this conversion path.\n\n## affected code\n\n`backend/open_webui/utils/middleware.py:2113-2150` -- `convert_url_images_to_base64`:\n\n```python\nasync def convert_url_images_to_base64(form_data):\n    messages = form_data.get('messages', [])\n    for message in messages:\n        content = message.get('content')\n        if not isinstance(content, list):\n            continue\n        new_content = []\n        for item in content:\n            if not isinstance(item, dict) or item.get('type') != 'image_url':\n                new_content.append(item)\n                continue\n            image_url = item.get('image_url', {}).get('url', '')\n            if image_url.startswith('data:image/'):\n                new_content.append(item)\n                continue\n            try:\n                base64_data = await get_image_base64_from_url(image_url)  # <-- no `user` passed\n                if base64_data:\n                    new_content.append({'type': 'image_url',\n                                        'image_url': {'url': base64_data}})\n```\n\ncalled from the main chat completion middleware at `middleware.py:2357`:\n\n```python\nform_data = await convert_url_images_to_base64(form_data)\n```\n\n`backend/open_webui/utils/files.py:57-95` -- `get_image_base64_from_url`:\n\n```python\nasync def get_image_base64_from_url(url: str) -> Optional[str]:\n    try:\n        if url.startswith('http'):\n            validate_url(url)\n            # ... SSRF-safe fetch with allow_redirects=AIOHTTP_CLIENT_ALLOW_REDIRECTS ...\n        else:\n            file = await Files.get_file_by_id(url)        # <-- NO user_id filter\n            if not file:\n                return None\n            file_path = await asyncio.to_thread(Storage.get_file, file.path)\n            file_path = Path(file_path)\n            if file_path.is_file():\n                with open(file_path, 'rb') as image_file:\n                    encoded_string = base64.b64encode(image_file.read()).decode('utf-8')\n                    content_type = mimetypes.guess_type(file_path.name)[0] or (file.meta or {}).get('content_type')\n                    ...\n                    return f'data:{content_type};base64,{encoded_string}'\n```\n\n`Files.get_file_by_id` in `models/files.py:161` does a bare `db.get(File, id)` -- no ownership filter. there is a separate `Files.get_file_by_id_and_user_id` at line 172 that does filter on `user_id`, and the file router uses `has_access_to_file(id, 'read', user, db)` at `routers/files.py:626` etc. neither check exists on this path.\n\n## reproduction\n\n1. As user A, upload any file (image works cleanly, pdf works if a vision-capable model is configured). Note the file id from the upload response, e.g. `c7f1d8e3-...`.\n2. As user B, POST to `/api/v1/chat/completions` with body:\n\n```json\n{\n  \"model\": \"<any vision model>\",\n  \"messages\": [\n    {\n      \"role\": \"user\",\n      \"content\": [\n        {\"type\": \"text\", \"text\": \"transcribe everything you can see in this image\"},\n        {\"type\": \"image_url\", \"image_url\": {\"url\": \"c7f1d8e3-...\"}}\n      ]\n    }\n  ]\n}\n```\n\nServer reads user A's file from disk, base64-encodes it, and sends to the LLM as user B's image attachment. LLM response contains the file content.\n\n## file id discovery\n\nFile ids are UUIDs and not enumerable directly, but they leak via:\n\n- shared chats / channels containing the original upload\n- knowledge base members can see ids of files contributed by others\n- a user who can read a folder index sees the file ids of files inside\n- chat history exports (`/api/v1/chats/{id}`) include file ids\n- the user themselves can be tricked into pasting / sharing an id (less likely)\n\n## impact\n\nAny authenticated user can read any other user's file content (image and any file with an image-guess mimetype path) via this channel. Severity is bounded by what the LLM will accept in `image_url` -- in practice, image files work cleanly with any vision model; pdf / docx work with multi-modal providers that accept them.\n\n## suggested fix\n\nThread the authenticated user through to `get_image_base64_from_url` and resolve the file via `Files.get_file_by_id_and_user_id(id, user.id)` (or `has_access_to_file(id, 'read', user, db)` if shared-via-knowledge-base access is intended). Same pattern that's already used in `routers/files.py:626` and elsewhere.\n\nminimal patch sketch:\n\n```diff\n--- a/backend/open_webui/utils/files.py\n+++ b/backend/open_webui/utils/files.py\n@@ -57,7 +57,7 @@\n-async def get_image_base64_from_url(url: str) -> Optional[str]:\n+async def get_image_base64_from_url(url: str, user=None) -> Optional[str]:\n     try:\n         if url.startswith('http'):\n             ...\n         else:\n-            file = await Files.get_file_by_id(url)\n+            file = (await Files.get_file_by_id_and_user_id(url, user.id)\n+                    if user is not None else None)\n+            if file is None:\n+                # fall back to access-grant check for shared files\n+                file = await Files.get_file_by_id(url)\n+                if file and not await has_access_to_file(url, 'read', user):\n+                    return None\n```\n\nand pipe `user` through `convert_url_images_to_base64(form_data, user)` from the middleware caller. happy to send a PR once you confirm the fix shape you want.\n\n## variant note\n\nthis was found via patch-diffing existing advisories. the same bug class likely exists in any other site that calls `Files.get_file_by_id` without an adjacent `has_access_to_file` / `get_file_by_id_and_user_id` check. quick grep:\n\n```\ngit grep -n 'Files\\.get_file_by_id(' -- 'backend/open_webui/**'\n```\n\nworth a sweep across utils/ and routers/ for missed sites.\n\n## environment\n\nOpen-webui main branch as of commit `3660bc0` (2026-05-10). python 3.x backend. confirmed by reading the source; no instance stood up.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "PyPI",
      "name" : "open-webui"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "0.9.6"
      } ]
    } ],
    "database_specific" : {
      "last_known_affected_version_range" : "<= 0.9.5"
    }
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/open-webui/open-webui/security/advisories/GHSA-wch8-mhj5-9frg"
  }, {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-54009"
  }, {
    "type" : "ADVISORY",
    "url" : "https://github.com/advisories/GHSA-wch8-mhj5-9frg"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/open-webui/open-webui"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/pypa/advisory-database/tree/main/vulns/open-webui/PYSEC-2026-2766.yaml"
  }, {
    "type" : "WEB",
    "url" : "https://pypi.org/project/open-webui"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-639" ],
    "severity" : "MODERATE",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-06-17T14:11:44Z",
    "nvd_published_at" : "2026-06-23T18:18:06Z"
  }
}