http2-specific-attacks

http2-specific-attacks is a skill for Claude Code, Codex from SecurityTalent/bugskill-ai. It costs 61 tokens per session (3,188 once invoked), scanned A, a copy of http2-specific-attacks, MIT.

A security testing guide for weaknesses specific to HTTP/2, a newer web protocol that sends requests in binary frames and can handle many streams at once. It focuses on differences between HTTP/2 and older HTTP/1.1 handling.

In plain words
What is it for?
It helps test HTTP/2 framing, header compression, stream multiplexing, protocol upgrades, and HTTP/2-to-HTTP/1.1 translation. It also covers request smuggling and race conditions that depend on HTTP/2 behavior.
Why use it?
It helps uncover flaws that ordinary web-request tests may miss when servers, proxies, and applications translate between protocol versions. These differences can affect request parsing, compression, routing, and timing.

Skill for Claude CodeCodex

Written for no agent in particular: nothing here depends on one.

Needs its repository: it reads a path above its own folder, which exists only inside the repository. The line is │ │ │ └── See ../request-smuggling/H2_SMUGGLING_VARIANTS.md.

Good fit It helps test HTTP/2 framing, header compression, stream multiplexing, protocol upgrades, and HTTP/2-to-HTTP/1.1 translation. It also covers request smuggling and race conditions that depend on HTTP/2 behavior.

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Install

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.

Clone the repo
git clone --depth 1 https://github.com/SecurityTalent/bugskill-ai
agentmods
npx agentmods add skills/securitytalent/bugskill-ai/http2-specific-attacks

Made for: Claude Code, Codex.

Wrote 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.

agentmods badge for http2-specific-attacks

README.md
[![agentmods](https://agentmods.dev/badge/skills/securitytalent/bugskill-ai/http2-specific-attacks/github.svg)](https://agentmods.dev/skills/securitytalent/bugskill-ai/http2-specific-attacks)
Your own site
<a href="https://agentmods.dev/skills/securitytalent/bugskill-ai/http2-specific-attacks"><img src="https://agentmods.dev/badge/skills/securitytalent/bugskill-ai/http2-specific-attacks/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.

agentmods 80×15 button for http2-specific-attacks

Your own site · 80×15
<a href="https://agentmods.dev/skills/securitytalent/bugskill-ai/http2-specific-attacks"><img src="https://agentmods.dev/badge/skills/securitytalent/bugskill-ai/http2-specific-attacks.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 61 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 3,188 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 1 finding. A grade says what 26 rules found in the file — not that it is safe.
Origin 100% copy Near-identical to another mod in the catalogue.
Token cost

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.

ModelPer sessionOnce invoked
Fable 5.1 $0.00061 $0.03188
Opus 5.5 $0.00024 $0.01275
Sonnet 5.5 $0.00012 $0.00638
Haiku 4.5 $0.00006 $0.00319

Measured 1mo ago against content hash b02b678fe8e7, method: parsed. Prices are Anthropic first-party input rates as of 2026-10-07, from the pricing page.

Security

Grade A, and why

http2-specific-attacks scanned grade A with 1 finding 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.

Makes network callslowCapability

Not a fault in itself. Listed so you know the mod talks to something, and to what.

curl -v --http1.1 https://target.com/ \
Origin

This is a copy

100% identical to http2-specific-attacks — 0 lines differ, which has more behind it and is treated as the original. This page carries a canonical link to it rather than competing with it.

Awesome-Claude-Code-Agent-Skills/02-Web-Application-Security/http2-specific-attacks/SKILL.md · 351 lines

How it starts

The opening of the file, as written. The whole thing — 351 lines — stays where its author put it; the contents beside it link to each section on GitHub.

SKILL: HTTP/2 Specific Attacks — Expert Attack Playbook

AI LOAD INSTRUCTION: HTTP/2 protocol-level attack techniques beyond basic request smuggling. Covers h2c smuggling, pseudo-header manipulation, HPACK attacks, single-packet race conditions, and H2→H1 downgrade injection. Base models conflate HTTP/2 smuggling with HTTP/1.1 smuggling — this skill focuses on H2-unique attack surface.


1. HTTP/2 ATTACK SURFACE OVERVIEW

Feature Attack Surface
Binary framing Frame-level manipulation, parser differentials
HPACK compression Compression oracles (CRIME/BREACH), table poisoning
Multiplexing Single-packet race conditions, RST_STREAM flood
Server push Cache poisoning via unsolicited push
Pseudo-headers (:method/:path/:authority/:scheme) Injection, request splitting, path discrepancy

2. h2c (HTTP/2 CLEARTEXT) SMUGGLING

2.1 Concept

h2c is HTTP/2 without TLS, negotiated via the HTTP/1.1 Upgrade mechanism. Many reverse proxies forward the Upgrade: h2c header without understanding it, allowing attackers to bypass proxy-level access controls.

Client ──[Upgrade: h2c]──> Reverse Proxy ──[forwards blindly]──> Backend
                                                                    │
                                                            Backend speaks H2
                                                            Proxy is blind to
                                                            the H2 conversation

Read the full file on GitHub · 351 lines

Changes

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.

  1. 1mo ago First seen · 351 lines · 61 tokens per session scan A b02b678fe8e7

Subscribe to this mod's changes

http2-specific-attacks is a skill published in the GitHub repository SecurityTalent/bugskill-ai (13 stars, last pushed 21d ago), licensed MIT. It adds 61 tokens to every session and 3,188 once invoked, about $0.0002 per session on Opus 5.5. A static security scan graded it A with 1 finding (makes network calls). It is 100% identical to http2-specific-attacks, differing in 0 lines, and is treated as a copy.

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