libafl

libafl is a skill for Claude Code, Codex from trailofbits/skills. It costs 91 tokens per session (4,496 once invoked), scanned D, original, CC-BY-SA-4.0.

A guide for building custom fuzzers with LibAFL, a modular Rust library for assembling fuzzing components. These components control how inputs run, change, and are evaluated.

In plain words
What is it for?
It is for creating bespoke fuzzers and mutators, testing non-standard targets or architectures, and combining custom observers, feedback, schedulers, and executors.
Why use it?
Standard fuzzing tools may not fit unusual targets or hardware; a modular library lets developers adapt the fuzzer to those constraints.

Skill for Claude CodeCodex

Written for Claude Code and Codex: shipped in a Claude Code plugin, but also agents/openai.yaml present.

Part of the testing-handbook-skills plugin — 15 skills shipped together

Good fit It is for creating bespoke fuzzers and mutators, testing non-standard targets or architectures, and combining custom observers, feedback, schedulers, and executors.

Compare 6 skills from other repositories ↓
Install with agentmods
npx agentmods add skills/trailofbits/skills/libafl
About the project

Trail of Bits Skills Marketplace is a collection of Claude Code plugins, skills, agents, commands, and instructions for security analysis, vulnerability detection, code auditing, and development workflows. It is for developers and security researchers using AI-assisted tools to inspect software, smart contracts, CI workflows, and related artifacts. The catalogue entries are examples of the marketplace’s reusable agent extensions.

trailofbits/skills · 6,988 stars · on GitHub

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.

Any agent
npx skills add trailofbits/skills --skill libafl
Clone the repo
git clone --depth 1 https://github.com/trailofbits/skills

Made for: Claude Code, Codex.

Or install testing-handbook-skills, the plugin that ships this one along with the rest of its 15 skills.

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 libafl

README.md
[![agentmods](https://agentmods.dev/badge/skills/trailofbits/skills/libafl.svg)](https://agentmods.dev/skills/trailofbits/skills/libafl)
Your own site
<a href="https://agentmods.dev/skills/trailofbits/skills/libafl"><img src="https://agentmods.dev/badge/skills/trailofbits/skills/libafl.svg" alt="Measured on agentmods" height="20"></a>
Per session 91 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 4,496 The whole file, excluding the scripts and references it only reads on demand.
Security scan D 3 findings. A grade says what 26 rules found in the file — not that it is safe. Third-party audits
  • Socket pass 18 Mar 2026
  • Snyk warn 17 Feb 2026
How audits are shown
Origin unknown No closer match found 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 $0.00091 $0.04496
Opus 5 $0.00046 $0.02248
Sonnet 5 $0.00018 $0.00899
Haiku 4.5 $0.00009 $0.00450

Measured 4d ago against content hash 2f7f261439c2, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-07, from the pricing page.

Security

Grade D, and why

libafl scanned grade D with 3 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 4d 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.

Asks for rootmediumPrivilege escalation

A mod that escalates privileges can change anything on the machine, not only the project.

sudo ./llvm.sh 15

Downloads and executes remote codehighSupply chain

curl | sh runs whatever the server returns today, which is not necessarily what it returned when this was reviewed.

curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | sh

Makes network callslowCapability

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

wget https://apt.llvm.org/llvm.sh
plugins/testing-handbook-skills/skills/libafl/SKILL.md · 624 lines

The source is not reproduced here

Licensed CC-BY-SA-4.0

The repository is licensed CC-BY-SA-4.0, which this catalogue does not treat as permission to reproduce the file. Read it at the source.

Read it on GitHub

Files

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.

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. 4d ago First seen · 624 lines · 91 tokens per session scan D 2f7f261439c2

Subscribe to this mod's changes

libafl is a skill published in the GitHub repository trailofbits/skills (6,988 stars, last pushed 4d ago), licensed CC-BY-SA-4.0. It adds 91 tokens to every session and 4,496 once invoked, about $0.0005 per session on Opus 5. A static security scan graded it D with 3 findings (asks for root, downloads and executes remote code, makes network calls). No closer match exists in the catalogue, so it is treated as the original; first seen 2026-09-03.

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