http2-specific-attacks

A security guide for attacking weaknesses specific to HTTP/2, the newer version of the web’s request-and-response protocol. It covers framing, header compression, multiplexed streams, and translation between HTTP/2 and HTTP/1.1.

In plain words
What is it for?
Testing HTTP/2 services for request smuggling, header and compression attacks, stream-race issues, cache poisoning, and downgrade flaws.
Why use it?
It helps distinguish HTTP/2-specific request attacks from older HTTP/1.1 techniques and explains how protocol differences can create vulnerabilities.

Skill for Claude CodeCodex

Install

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.

agentmods
npx agentmods add skills/miru-zero/zero-brain/http2-specific-attacks
Any agent
npx skills add miru-zero/zero-brain --skill http2-specific-attacks
Clone the repo
git clone --depth 1 https://github.com/miru-zero/zero-brain

Made for: Claude Code, Codex.

Per session 61 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 3,212 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 1 finding. Scan, not verified.
Origin 92% 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 $0.00061 $0.03212
Opus 5 $0.00030 $0.01606
Sonnet 5 $0.00012 $0.00642
Haiku 4.5 $0.00006 $0.00321

Measured yesterday against content hash cd383f6aa09f, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, 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 yesterday.

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

92% identical to http2-specific-attacks — 4 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.

skills/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. yesterday First seen · 351 lines · 61 tokens per session scan A cd383f6aa09f

Subscribe to this mod's changes

http2-specific-attacks is a skill published in the GitHub repository miru-zero/zero-brain (0 stars, last pushed 14d ago), licensed MIT. It adds 61 tokens to every session and 3,212 once invoked, about $0.0003 per session on Opus 5. A static security scan graded it A with 1 finding (makes network calls). It is 92% identical to http2-specific-attacks, differing in 4 lines, and is treated as a copy.

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