GitHub Security Advisory: GHSA-7r82-qhg4-6wvj
Package: open-webui (PIP)
Severity: HIGH (CVSS 8.1)
CWE: CWE-862: Missing Authorization
Vulnerable versions: <= 0.8.12
Patched in: 0.9.0

Summary: Open WebUI has Knowledge Base Destruction and RAG Poisoning via Unauthorized Collection Overwrite

Details:
# Knowledge Base Destruction and RAG Poisoning via Unauthorized Collection Overwrite

## Affected Component

Retrieval web/YouTube processing endpoints:
- `backend/open_webui/routers/retrieval.py` (lines 1810-1837, `process_web`)
- `backend/open_webui/routers/retrieval.py` (the parallel `process_youtube` endpoint)
- `backend/open_webui/routers/retrieval.py` (line 1445, `save_docs_to_vector_db` call chain)

## Affected Versions

Current main branch (commit `6fdd19bf1`) and likely all versions with RAG/knowledge base functionality.

## Description

The `POST /api/v1/retrieval/process/web` endpoint accepts a user-supplied `collection_name` and an `overwrite` query parameter (default: `True`). It performs no authorization check on whether the calling user owns or has write access to the target collection. When `overwrite=True`, `save_docs_to_vector_db` calls `VECTOR_DB_CLIENT.delete_collection()` on the target collection before writing new content.

Combined with the knowledge base enumeration vulnerability (separate report), an attacker can trivially discover any user's knowledge base UUID and then destroy or poison it.

```python
# retrieval.py:1810-1837 — no collection authorization check
@router.post('/process/web')
async def process_web(
    request: Request,
    form_data: ProcessUrlForm,
    user=Depends(get_verified_user),
    ...
):
    # ... fetch and process the URL ...
    save_docs_to_vector_db(
        request=request,
        docs=docs,
        collection_name=form_data.collection_name,  # attacker-controlled, unchecked
        overwrite=overwrite,                        # defaults to True
        ...
    )
```

## CVSS 3.1 Breakdown

| Metric | Value | Rationale |
|--------|-------|-----------|
| Attack Vector | Network (N) | Exploited remotely via API call |
| Attack Complexity | Low (L) | Single API call with a known KB UUID |
| Privileges Required | Low (L) | Requires any authenticated user account |
| User Interaction | None (N) | No victim interaction required |
| Scope | Unchanged (U) | Impact within the knowledge base authorization boundary |
| Confidentiality | None (N) | No data disclosure from this vulnerability directly |
| Integrity | High (H) | Complete replacement of victim's KB content with attacker-controlled data |
| Availability | High (H) | Victim's original KB embeddings are deleted; KB effectively destroyed |

## Attack Scenario

1. Attacker discovers victim's KB UUID via the `knowledge-bases` meta-collection (separate finding) or other enumeration.
2. Attacker sends:
   ```
   POST /api/v1/retrieval/process/web?overwrite=true
   {
     "url": "https://attacker.com/poison",
     "collection_name": "<victim_kb_uuid>"
   }
   ```
3. The endpoint fetches content from the attacker's URL.
4. `save_docs_to_vector_db` deletes the entire vector collection belonging to the victim's knowledge base.
5. The attacker's fetched content is embedded and written as the new collection content.
6. Victim's RAG queries against their