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Get Started Free →elementalsouls/hunt-http-smuggling
Hunt HTTP request smuggling (CL.TE, TE.CL, H2.CL, H2.TE). Cause: front-end proxy and back-end server disagree on where one request ends and the next begins (Content-Length vs Transfer-Encoding header parsing inconsistency). CL.TE: front-end uses CL, back uses TE → smuggle by sending TE: chunked but with body that fits CL count. TE.CL: opposite. H2.CL: HTTP/2 downgrade, smuggle CL into HTTP/1.1 back-end. Detection tools: Burp HTTP Request Smuggler extension, smuggler.py, h2csmuggler. Confirm: tim
Passed 20 of 23 test cases with the skill, and 14 of 23 without it.
and 5 more in the full report
6 fixed14 passed either way3 still failing0 broke
Tokens, turns and time describe resource use, not a dollar price.
One of 6 test cases the skill fixed. Same model, same prompt, with and without the skill.
We are auditing an environment running Nginx 1.25 as an edge reverse proxy in front of Python Gunicorn application servers. The team wants to run classic CL.TE and TE.CL payload suites against Nginx. What is the expected behavior and what protocol testing direction should be pursued? Provide a brief technical recommendation.
| Checked | Without skill | With skill |
|---|---|---|
| states that Nginx 1.21+ rejects requests combining Content-Length and Transfer-Encoding headers with HTTP 400 | Missed | Passed |
| recommends testing H2 downgrade desynchronization vectors when HTTP/2 is enabled | Passed | Passed |
The instructions your model reads when the skill loads.
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 |
test cases passed, vs 14 / 23 without
More skills from the same source and nearby in the registry, with their headline benchmark lift.