⚠️ AUTHORIZED USE ONLY This skill is for educational purposes or authorized security assessments only. You must have explicit, written permission from the system owner before using this tool. Misuse of this tool is illegal and strictly prohibited.
Mandatory confirmation gate Before running any command that probes, exploits, changes, persists on, extracts data from, or attempts credential access against a target:
- Ask the user to state the exact target URL, IP, account, or resource.
- Ask the user to confirm written authorization and the permitted scope.
- Show the exact command(s) and explain their expected effect.
- Wait for explicit confirmation in the current conversation.
Without that confirmation, remain read-only and provide defensive guidance only. Prefer a sandbox, disposable VM, or controlled lab.
Lowest dup rate. $5K–$30K. PortSwigger research by James Kettle.
POST / HTTP/1.1
Content-Length: 13
Transfer-Encoding: chunked
0
SMUGGLED
1. Burp extension: HTTP Request Smuggler
2. Right-click request → Extensions → HTTP Request Smuggler → Smuggle probe
3. Manual timing: CL.TE probe + ~10s delay = backend waiting for rest of body
Poison next request → access admin as victim
Steal credentials → capture victim's session
Cache poisoning → stored XSS at scale
The classic CL.TE / TE.CL payloads are NOT universally exploitable in 2026. Modern proxies are RFC 9112 strict by default. Fingerprint the front-end BEFORE investing time.
| Front-end | CL.TE | TE.CL | H2.CL | H2.TE | Notes |
|---|---|---|---|---|---|
| Nginx ≥ 1.21 | NO | NO | partial (H2 ingress) | partial | RFC-strict; rejects CL+TE with HTTP 400. Verified locally on Nginx 1.27 — all 9 documented variants killed by front-end (docs/verification/phase2h-smuggling-cachepoison.md). |
| Caddy 2.x | NO | NO | — | — | Hardened by default |
| Envoy ≥ 1.20 | NO | NO | partial | partial | Hardened in most paths |
| HAProxy ≤ 2.4 | ✓ | ✓ | — | — | Vulnerable, see CVE-2021-40346 |
| AWS ALB + specific upstream | partial | partial | ✓ | ✓ | Several disclosed-paid reports 2022-2024 |
| Cloudflare → S3 / Lambda chains | — | — | ✓ | ✓ | H2-downgrade attacks remain viable |
| Older F5 BIG-IP (TMM < 16) | ✓ | — | — | — | Vendor advisories |
| Citrix ADC / NetScaler (older firmware) | ✓ | ✓ | — | — | Disclosed in 2020-2022 |
| Squid 3.x | ✓ | — | — | — | Older deployments |
| Apache Traffic Server (older) | ✓ | ✓ | ✓ | ✓ | PortSwigger research |
| Apache mod_proxy_ajp → Tomcat | — | — | — | — | Cross-protocol HTTP→AJP desync (CVE-2022-26377); smuggled request is opaque to the WAF and reaches internal AJP admin/status paths that lack the external auth controls |
| Custom Python / Go proxies | ✓ | ✓ | — | — | Frequently miss RFC enforcement |
curl -sI https://target/ | grep -i "Server:"
nginx/1.21+, Caddy, envoy → CL/TE classic is dead — pivot to H2.CL/H2.TE if the front-end speaks HTTP/2, or look for legacy proxies upstreamHAProxy, header points to AWS/CDN → run the full payload matrixspace-before-colon probe; if it doesn't 400, dig deeperH2-downgrade smuggling attacks rely on the front-end speaking HTTP/2 to the client and HTTP/1.1 to origin. The downgrade introduces CL/TE confusion because HTTP/2's frame-length headers don't survive the conversion cleanly. Most CDN+origin chains in 2024-2026 use this exact topology.
Tools that send HTTP/2 raw frames (Burp Pro's HTTP Request Smuggler extension, h2csmuggler, smuggler.py) are the right starting point against CDN-fronted targets. Avoid HTTP/1.1-only test clients (curl, raw sockets) against H2-front-ended targets — you'll send the wrong protocol entirely.
The highest-impact smuggling outcome needs no per-victim interaction. Instead of blindly poisoning the queue, smuggle a request aimed at a back-end handler that echoes the full request — a search endpoint that reflects headers, or a redirect that mirrors the request line. The next victim's headers (Cookie, Authorization, X-Access-Token) get attributed to your smuggled request, and the reflecting handler returns them in a response you read. Repeated on a busy keep-alive socket, this harvests live credentials from arbitrary users at scale — and it works even through a CDN (Akamai/Cloudflare) when the CDN↔origin hop desyncs. Chains to hunt-ato.
hunt-cache-poison — Smuggling + cache is the canonical critical chain; one smuggled request becomes the cached response for every subsequent victim. Chain primitive: CL.TE smuggle a request whose response body contains attacker HTML/JS → front-end cache stores it under a popular URL (/, /login) → de-sync poisoning where the smuggled request becomes the cached response for the next N victims, persisting for the cache TTL.hunt-auth-bypass — Smuggling reaches internal-only routes that the front-end WAF/auth-proxy filters out. Chain primitive: smuggle GET /admin/users HTTP/1.1 past the front-end ACL that blocks external /admin/* → backend processes the smuggled request as if from a trusted internal source → bypass front-end auth by smuggling internal-routed request → admin data in the response queue.hunt-idor — Smuggling attaches the NEXT user's session cookies to an attacker-controlled request path. Chain primitive: smuggle GET /api/me HTTP/1.1 with no cookies → backend pairs it with the next legitimate user's incoming connection cookies → victim's session cookie attached to attacker's smuggled request → attacker reads the response containing victim's PII/tokens.hunt-xss — Smuggling injects XSS payloads into the response stream of the next victim without ever appearing in a URL parameter. Chain primitive: smuggled request body contains reflected payload that the backend renders into the next response in the queue → next visitor to / receives attacker HTML inline → reflected XSS at every visitor without any URL parameter visible to them or to logs.security-arsenal — Reach for the smuggling payload bank (CL.TE / TE.CL / TE.TE obfuscations, H2.CL downgrade probes, h2csmuggler one-liners, Burp HTTP Request Smuggler extension config) and the time-delay confirmation template before manual hex-editing.triage-validation — Run the Pre-Severity Gate before claiming Critical: the smuggled-request effect MUST land on a request issued by a different client/session, not your own follow-up. A timing delta in your own browser alone is parser disagreement, not exploitable smuggling.triage-validation) before reporting; report via report-writing. Prefer a sandbox, disposable VM, or controlled lab.# Read-only first step; confirm scope before anything active.
cat scope.txt # target list from the authorized engagement brief
Adapted from elementalsouls/Claude-BugHunter (MIT); frontmatter, When to Use/Limitations, and safety boundaries added for upstream compliance. Docs-only import: executable helpers, commands, engine, and research assets not bundled.