OpenClaw Canvas Authentication Bypass Vulnerability

ZDI-CAN-29311: OpenClaw Canvas Authentication Bypass Vulnerability

-- ABSTRACT -------------------------------------

Trend Micro's Zero Day Initiative has identified a vulnerability affecting the following products: OpenClaw - OpenClaw

-- VULNERABILITY DETAILS ------------------------

• Version tested: openclaw 2026.2.17
• Platform tested: macOS 26.3

Analysis

Description

The OpenClaw gateway's authorizeCanvasRequest() function implements an IP-based authentication fallback for canvas endpoints (/__openclaw__/a2ui/, /__openclaw__/canvas/, /__openclaw__/ws). When a WebSocket client authenticates from a private IP address, ALL subsequent HTTP requests from that same IP are granted canvas access without requiring their own authentication token.

In environments where multiple clients share a single IP address ��� corporate NAT, VPN concentrators, Kubernetes clusters, Docker host-mode networking ��� an unauthenticated attacker on the same network is granted full canvas access by virtue of sharing an IP with a legitimate authenticated client.

Root Cause

Three functions in src/gateway/server-http.ts create this vulnerability:

1. IP-matching function (line ~100)

function hasAuthorizedWsClientForIp(clients: Set<GatewayWsClient>, clientIp: string): boolean {
  for (const client of clients) {
    if (client.clientIp && client.clientIp === clientIp) {
      return true;
    }
  }
  return false;
}

This function checks if ANY connected WebSocket client shares the same IP. It does not verify that the HTTP request belongs to the same user, session, or browser as the WS client.

2. IP-based fallback in authorizeCanvasRequest (line ~109)

async function authorizeCanvasRequest(params: { ... }): Promise<GatewayAuthResult> {
  // ... token check first ...

  const clientIp = resolveGatewayClientIp({ ... });

  // Only allow fallback for private/loopback addresses
  if (!isPrivateOrLoopbackAddress(clientIp)) {
    return lastAuthFailure ?? { ok: false, reason: "unauthorized" };
  }

  // THE VULNERABILITY: grants access based on IP alone
  if (hasAuthorizedWsClientForIp(clients, clientIp)) {
    return { ok: true };
  }

  return lastAuthFailure ?? { ok: false, reason: "unauthorized" };
}

If the HTTP request comes from a private IP that matches any authenticated WS client, access is granted without verifying the request's own credentials.

3. Canvas path routing

function isCanvasPath(pathname: string): boolean {
  return (
    pathname === A2UI_PATH ||              // /__openclaw__/a2ui
    pathname.startsWith(`${A2UI_PATH}/`) ||
    pathname === CANVAS_HOST_PATH ||        // /__openclaw__/canvas
    pathname.startsWith(`${CANVAS_HOST_PATH}/`) ||
    pathname === CANVAS_WS_PATH            // /__openclaw__/ws
  );
}

All canvas endpoints use this weaker authentication path instead of the standard authorizeGatewayConnect() which requires a valid token.

Attack Scenario

Corporate NAT Environment

1. A company runs an OpenClaw gateway on an internal server with --bind lan and a token for authentication.
2. Developer Alice connects her OpenClaw desktop app via WebSocket using her valid token. The gateway records her IP as the corporate NAT address (e.g., 10.0.0.1).
3. Attacker Bob, on the same corporate network, also appears as 10.0.0.1 to the gateway (NAT).
4. Bob sends an HTTP request to http://gateway:18789/__openclaw__/a2ui/ with NO authentication header.
5. authorizeCanvasRequest() checks: Is 10.0.0.1 a private IP? Yes. Is there a WS client from 10.0.0.1? Yes (Alice). Access granted.
6. Bob now has full access to all canvas endpoints ��� the A2UI interface, canvas content, and the canvas WebSocket ��� without ever authenticating.

Kubernetes / Docker Environments

In containerized deployments using shared networking (host mode, pod networking), multiple containers share the same IP. One container's authentication enables canvas access for all containers on that IP.

Reproduction Steps

Prerequisites

• Docker installed
• Python 3
• OpenClaw Docker image built as openclaw:local

Steps

1. Navigate to the PoC directory and start the environment:

   cd vulnerabilities/04-canvas-ip-auth-bypass
   docker compose up -d --wait
   

2. This starts two containers on a shared Docker network:

   • Gateway (172.28.0.10): Token-protected OpenClaw gateway
   • Legitimate client (172.28.0.20): Connects via WebSocket with valid token, establishing IP trust

3. Wait a few seconds for the legitimate client to authenticate, then run the PoC:

   python3 poc.py
   

4. The PoC runs three tests:

   Test	Source	Source IP	Token	Result
   1 ��� Host (different IP)	Host machine	Host bridge IP	None	401 Unauthorized
   2 ��� Host with token (control)	Host machine	Host bridge IP	Valid	200 OK
   3 ��� Same IP (exploit)	docker exec into legit container	172.28.0.20	None	200 OK

5. Test 3 is the exploit: poc.py uses docker exec to run an HTTP request from inside the legitimate client's container (IP 172.28.0.20) with no Authorization header. The gateway's authorizeCanvasRequest() matches the source IP against the authenticated WebSocket client and returns 200 OK ��� granting full canvas access without credentials.

6. Cleanup:

   docker compose down -v
   

Impact

• Authentication Bypass: Any unauthenticated client sharing an IP with a legitimate WS-authenticated client gains full canvas endpoint access.
• Information Disclosure: Canvas endpoints serve:
  • The A2UI (Agent-to-User Interface) rendered content, which may contain sensitive data the AI agent is presenting to the user
  • The canvas HTML/JS application
  • The canvas WebSocket upgrade endpoint
• Scope: Affects all deployments where the gateway is network-exposed (--bind lan) and clients share IP addresses (NAT, VPN, K8s, corporate networks).
• No auth required: The attacker needs only network adjacency; no credentials, tokens, or user interaction.

-- CREDIT --------------------------------------- This vulnerability was discovered by: Peter Girnus (@gothburz) and Project AESIR of TrendAI Zero Day Initiative

-- FURTHER DETAILS ------------------------------

Supporting files: ZDI-CAN-29311.zip

If supporting files were contained with this report they are provided within a password protected ZIP file. The password is the ZDI candidate number in the form: ZDI-CAN-XXXX where XXXX is the ID number.

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http://www.zerodayinitiative.com/documents/disclosures-pgp-key.asc

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-- DISCLOSURE POLICY ----------------------------

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Fix Commit(s)

• c45f3c5b004c8d63dc0e282e2176f8c9355d24f1