Getting it into your agent
One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.
npx skills add UnboundCompute/security-agent-skills --skill hunting-http-request-smuggling-and-desyncgit clone --depth 1 https://github.com/UnboundCompute/security-agent-skillsWrote 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/unboundcompute/security-agent-skills/hunting-http-request-smuggling-and-desync)<a href="https://agentmods.dev/skills/unboundcompute/security-agent-skills/hunting-http-request-smuggling-and-desync"><img src="https://agentmods.dev/badge/skills/unboundcompute/security-agent-skills/hunting-http-request-smuggling-and-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/unboundcompute/security-agent-skills/hunting-http-request-smuggling-and-desync"><img src="https://agentmods.dev/badge/skills/unboundcompute/security-agent-skills/hunting-http-request-smuggling-and-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 | $0.00173 | $0.02085 |
| Opus 5.5 | $0.00069 | $0.00834 |
| Sonnet 5.5 | $0.00035 | $0.00417 |
| Haiku 4.5 | $0.00017 | $0.00209 |
Grade A, and why
hunting-http-request-smuggling-and-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 1mo 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.
How it starts
The opening of the file, as written. The whole thing — 135 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Hunting HTTP request smuggling and desync: when two parsers disagree on where a request ends
Request smuggling is a disagreement bug, not a parsing bug in isolation. When a request passes through more than one HTTP processor, a proxy or load balancer in front of an origin, each one has to decide where one request ends and the next begins, and if they decide differently, an attacker can hide a second request inside the first. The classic lever is conflicting length signals: a Content-Length and a Transfer-Encoding header, or two of either, that the front end and back end resolve in opposite orders. The consequence is severe because these connections are reused: a smuggled prefix left on a keep-alive connection prepends to the next user's request, so it poisons other people's traffic, bypasses front-end access controls, and captures requests. The hunt is about the seam between two parsers, so you look for where their framing rules differ. You hunt this by finding chained processors and testing whether a crafted request desyncs them.
When to use
- A request passes through more than one HTTP/1.1 processor: a proxy or load balancer in front of an origin.
- The processors may resolve Content-Length, Transfer-Encoding, or duplicate framing headers differently.
- Keep-alive connections are reused across requests, so a desync poisons the next request on the connection.
Scope check
Test smuggling only against systems you own or are authorized to assess, on non-production endpoints. A successful desync poisons other users' requests on a shared connection, so use a dedicated test origin, keep payloads benign, and never capture or alter real users' traffic. If you can't name the authorization, stop.
The loop
- Establish the processor chain first. Identify every HTTP processor on the path and their order: the front-end proxy or load balancer, any intermediate cache, and the origin. This is the false-positive killer: a single processor, or a chain that speaks a framing-unambiguous protocol end to end and rejects conflicting length signals, cannot desync. Name the chain, then look for framing disagreement between adjacent hops.
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.
- 1mo ago First seen · 135 lines · 173 tokens per session scan A e3aa5824c8e8
hunting-http-request-smuggling-and-desync is a skill published in the GitHub repository UnboundCompute/security-agent-skills (5 stars, last pushed 1mo ago), licensed MIT. It adds 173 tokens to every session and 2,085 once invoked, about $0.0007 per session on Opus 5.5. 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 2026-09-05.
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