Open WebUI is a self-hosted artificial intelligence platform designed to operate entirely offline. Prior to 0.9.0, the POST /api/v1/models/import endpoint allows users with the workspace.models_import permission to overwrite any existing model in the database, regardless of ownership. When an imported model's ID matches an existing model, the endpoint merges the attacker's payload over the existing model data and writes it to the database with no ownership or access grant validation. Additionally, filter_allowed_access_grants is never called, bypassing the access grant restrictions enforced on all other model mutation endpoints. This vulnerability is fixed in 0.9.0.

Affected: PyPI: open-webui

# Model Import Overwrites Any Model Without Ownership Check

## Affected Component

Model import endpoint: - `backend/open_webui/routers/models.py` (lines 254-308, `import_models`)

## Affected Versions

Current main branch (commit `6fdd19bf1`) and likely all versions with model import functionality.

## Description

The `POST /api/v1/models/import` endpoint allows users with the `workspace.models_import` permission to overwrite any existing model in the database, regardless of ownership. When an imported model's ID matches an existing model, the endpoint merges the attacker's payload over the existing model data and writes it to the database with no ownership or access grant validation. Additionally, `filter_allowed_access_grants` is never called, bypassing the access grant restrictions enforced on all other model mutation endpoints.

```python # Line 280 — fetches existing model with NO ownership check existing_models_dict = {m.id: m for m in Models.get_models_by_ids(model_ids, db=db)}

# Line 295 — attacker's data overrides existing model fields form = ModelForm(**{**existing_model.model_dump(), **model_data})

# Line 296 — writes directly, never calls filter_allowed_access_grants Models.update_model_by_id(model_id, form, db=db) ```

Compare with properly-guarded endpoints: - `update_model_by_id` (line 499): checks ownership/write access AND calls `filter_allowed_access_grants` - `update_model_access_by_id` (line 571): checks ownership/write access AND calls `filter_allow…

Affected: PyPI: open-webui

# Model Import Overwrites Any Model Without Ownership Check

## Affected Component

Model import endpoint: - `backend/open_webui/routers/models.py` (lines 254-308, `import_models`)

## Affected Versions

Current main branch (commit `6fdd19bf1`) and likely all versions with model import functionality.

## Description

The `POST /api/v1/models/import` endpoint allows users with the `workspace.models_import` permission to overwrite any existing model in the database, regardless of ownership. When an imported model's ID matches an existing model, the endpoint merges the attacker's payload over the existing model data and writes it to the database with no ownership or access grant validation. Additionally, `filter_allowed_access_grants` is never called, bypassing the access grant restrictions enforced on all other model mutation endpoints.

```python # Line 280 — fetches existing model with NO ownership check existing_models_dict = {m.id: m for m in Models.get_models_by_ids(model_ids, db=db)}

# Line 295 — attacker's data overrides existing model fields form = ModelForm(**{**existing_model.model_dump(), **model_data})

# Line 296 — writes directly, never calls filter_allowed_access_grants Models.update_model_by_id(model_id, form, db=db) ```

Compare with properly-guarded endpoints: - `update_model_by_id` (line 499): checks ownership/write access AND calls `filter_allowed_access_grants` - `update_model_access_by_id` (line 571): checks ownership/write access AND calls `filter_allow…