Getting it into your agent
It runs from inside its repository, so the clone comes first — what it calls does not travel with the file alone.
git clone --depth 1 https://github.com/ShulkwiSEC/bb-hugenpx agentmods add skills/shulkwisec/bb-huge/http-request-smuggling-desyncWrote this? Show the measurements
A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.
[](https://agentmods.dev/skills/shulkwisec/bb-huge/http-request-smuggling-desync)<a href="https://agentmods.dev/skills/shulkwisec/bb-huge/http-request-smuggling-desync"><img src="https://agentmods.dev/badge/skills/shulkwisec/bb-huge/http-request-smuggling-desync/github.svg" alt="Measured on agentmods" height="20"></a>Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.
<a href="https://agentmods.dev/skills/shulkwisec/bb-huge/http-request-smuggling-desync"><img src="https://agentmods.dev/badge/skills/shulkwisec/bb-huge/http-request-smuggling-desync.svg" alt="Reviewed on agentmods" width="80" height="20"></a>What it costs to keep this loaded
Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.
| Model | Per session | Once invoked |
|---|---|---|
| Fable 5.1 | $0.00066 | $0.02227 |
| Opus 5 | $0.00033 | $0.01113 |
| Sonnet 5 | $0.00013 | $0.00445 |
| Haiku 4.5 | $0.00007 | $0.00223 |
Grade A, and why
http-request-smuggling-desync scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 7d ago.
A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.
Nothing flagged
None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.
Copies of this mod
1 near-identical copy found in the catalogue:
- http-request-smuggling-desync — 100% identical, 0 lines differ
How it starts
The opening of the file, as written. The whole thing — 227 lines — stays where its author put it; the contents beside it link to each section on GitHub.
HTTP Request Smuggling (Desync Attacks)
When to Use
- When the target application architecture involves a front-end load balancer, reverse proxy, or CDN (e.g., Cloudflare, HAProxy, AWS ALB) mapping to a diverse back-end server.
- When you need to bypass a front-end WAF or access restricted internal administration panels.
- To execute high-impact attacks against other users, such as capturing their HTTP requests containing session cookies, or poisoning the front-end cache with malicious responses.
Prerequisites
- Authorized scope and target URLs from bug bounty program
- Burp Suite Professional (or Community) configured with browser proxy
- Familiarity with OWASP Top 10 and common web vulnerability classes
- SecLists wordlists for fuzzing and enumeration
Workflow
Phase 1: Identifying the Infrastructure Flaw
# Concept: HTTP/1.1 allows specifying request boundaries via Content-Length (CL) OR
# Transfer-Encoding: chunked (TE). If you send BOTH headers, and the Front-end and
# Back-end servers prioritize different ones, they will disagree on where the request ends.
# Requirement: You must carefully manipulate line endings (`\r\n`). Do not let tools
# auto-update your Content-Length header!
# 1. Probing for CL.TE (Front-end uses CL, Back-end uses TE)
# If vulnerable to CL.TE, this request triggers a timeout or severe delay.
POST / HTTP/1.1
Host: target.com
Content-Length: 4
Transfer-Encoding: chunked
1
Z
Q
# Explanation: Front-end reads 4 bytes ("1\r\nZ"). Back-end reads chunked encoding,
# sees chunk size 1 ('Z'), then expects the next chunk size but gets 'Q'. It hangs waiting for termination.
# 2. Probing for TE.CL (Front-end uses TE, Back-end uses CL)
POST / HTTP/1.1
Host: target.com
Content-Length: 6
Transfer-Encoding: chunked
0
X
# Explanation: Front-end reads chunks, sees 0 (end of chunk), forwards request.
# Back-end reads Content-Length 6. It reads past the "0\r\n\r\n" and waits for 'X' to complete the 6 bytes.
Phase 2: Exploitation - CL.TE Bypassing Front-End Controls
What ships with it
2 files beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.
What this file has done since we first saw it
Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.
- 7d ago First seen · 227 lines · 66 tokens per session scan A 828a87fee046
http-request-smuggling-desync is a skill published in the GitHub repository ShulkwiSEC/bb-huge (22 stars, last pushed 2mo ago), licensed MIT. It adds 66 tokens to every session and 2,227 once invoked, about $0.0003 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-09-03.
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http-request-smuggling-desync
Identify and exploit HTTP Request Smuggling (HTTP Desync) vulnerabilities caused by discrepancies in how front-end proxies (load balancers, CDNs) and back-end servers parse the Content-Length and Transfer-Encoding headers. Use this to bypass security controls, hijack user sessions, and poison web caches.
http-request-smuggling-te-te
Exploit advanced HTTP Request Smuggling combining Transfer-Encoding vulnerabilities (TE.TE). By obscuring the Transfer-Encoding header, an attacker forces desynchronization between a frontend proxy (which processes the request one way) and the backend server (which processes it another way), allowing the smuggling of…
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