Affected: open-webui

Open WebUI is a self-hosted artificial intelligence platform designed to operate entirely offline. Prior to 0.9.6, 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. This vulnerability is fixed in 0.9.6.

Affected: PyPI: open-webui

## 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: M…