Guide · Agent skill
How to use the Offensive Fuzzing Methodology agent skill
Updated · written with AI from the project's own documentation and checked against our catalogue data
The offensive-fuzzing skill is a written methodology that gives an AI agent a structured playbook for fuzz testing: choosing a fuzzer, writing a harness, building a seed corpus, running a campaign and triaging crashes. It is aimed at security researchers, developers working on C or C++ code, and students who already know the command line, compilers and debuggers. After this guide you will know what the skill does, how to install it, how to ask for it in plain language, and what you need before using it.
Offensive Fuzzing MethodologySnailSploit/Claude-Red · MIT Download the skill Quick start
- 1Download the ZIP. Get the offensive-fuzzing skill ZIP from this page.
- 2Unzip into a skills folder. Extract it into ~/.claude/skills/ for personal use or into a project's .claude/skills/ folder.
- 3Or upload in the Claude apps. Go to Settings → Capabilities → Skills and upload the skill.
- 4Install the fuzzers and toolchain. Install AFL++, libFuzzer through Clang, CMake and sanitizers separately.
- 5Describe the fuzzing job. Name the target, its input type and whether you have source code.
- 6Review commands and run. Check each suggested command, then run the campaign in an isolated environment.
- 7Triage the crashes. Minimise, symbolise and group crashes before writing any report.
What the offensive-fuzzing skill makes the agent do
Fuzzing means automatically feeding large numbers of malformed or random inputs to a program to find inputs that make it crash or misbehave. The skill gives the agent a step-by-step workflow for that job: research the target, choose analyses, build a harness, seed a corpus, instrument and build, fuzz, triage crashes and report.
The skill covers several fuzzer types (BlackBox, GreyBox, Snapshot, WhiteBox and Ensemble) and names tools such as AFL++, libFuzzer, Honggfuzz, Boofuzz and syzkaller. It also includes reference material on sanitizers and test oracles, such as ASan, UBSan and KASAN, and specialised notes for kernel, EDR and Rust targets. It is framed around offensive work, so it leans toward finding exploitable bugs rather than only hardening code.
Install the offensive-fuzzing skill
Option 1, personal skills folder: download the ZIP for this skill from this page and unzip it into ~/.claude/skills/ so that the SKILL.md file sits inside an offensive-fuzzing folder.
Option 2, single project: unzip the ZIP into the .claude/skills/ folder of your project so the skill applies only there.
Option 3, Claude apps: upload the skill under Settings → Capabilities → Skills.
Install the tools the skill depends on
The skill does not ship the fuzzers. You install them separately. The skill expects AFL++, libFuzzer (through Clang), Honggfuzz, Boofuzz, syzkaller or the other fuzzers named in the guide, plus a C or C++ toolchain with Clang and CMake and sanitizers such as ASan and UBSan.
For kernel work the skill also expects a QEMU VM setup, and you need access to the target's source or binary.
- AFL++, libFuzzer (Clang), Honggfuzz, Boofuzz, syzkaller: installed separately
- Clang, CMake and a C/C++ toolchain
- Sanitizers such as ASan and UBSan
- Target source or binary, plus QEMU for kernel work
How to trigger the skill with natural requests
You do not need a special command. Describe the fuzzing job in plain language and name the target. The skill's description covers setting up or running fuzz campaigns against file parsers, network protocols, kernel drivers, EDR engines, embedded firmware and language runtimes, so requests that mention those areas are the most likely to use it.
Include the context the agent needs: the target's language, whether you have source code, and whether you are fuzzing a file parser, a protocol or a driver.
- Set up an AFL++ fuzz campaign for this C file parser. I have the source and want ASan enabled.
- Write a libFuzzer harness for the function that parses this config format.
- My AFL++ run has stalled after an hour. What should I change?
- Triage these crash files: minimise them, symbolise the stack traces and group duplicates.
Work through an example workflow
A typical session follows the skill's core workflow. The agent first maps input surfaces and high-value code, then builds the target with instrumentation. It writes a harness, for example a libFuzzer entry point that passes the input bytes to your parser.
Next it builds a seed corpus, minimises it with afl-cmin and launches the campaign. When crashes appear, it minimises each one with afl-tmin, symbolises it with sanitizer options and groups duplicates for review.
LLVMFuzzerTestOneInput(const uint8_t* data, size_t size) { parse_or_process(data, size); return 0; }Monitor progress and triage crashes
If a campaign stops finding new paths, the skill suggests enabling CmpLog, adding a dictionary, switching to directed fuzzing, using concolic assistance on hard branches or snapshotting the target to increase executions per second.
For triage, the skill's sequence is minimise, symbolise, then hash and bucket crashes. It also lists sanitizer option strings for ASan, UBSan, TSan and MSan.
afl-tmin -i crash -o crash.min -- ./target @@Safety notes: scripts and network
Only test systems you own or have written authorisation to test. The skill is framed around attacking targets, and running fuzzers can be disruptive or illegal without permission.
The skill does not run scripts and does not use the network by itself. Commands it suggests, such as running fuzzers or setting up a VM, are executed by you or the agent in your environment, so review them before running. Fuzzers can consume a lot of CPU and disk space, so run them on isolated machines.
- Use only on targets you are authorised to test
- Review every suggested command before it runs
- Run long campaigns in an isolated environment
Tips for getting better results
Give the agent a precise target and the input format. Good seed corpora matter more than clever mutation, so ask for seeds from the test suite or sample files. Build with sanitizers, because they turn silent memory corruption into a clear crash report.
- Start with one fuzzer and one target before running an ensemble
- Keep your raw corpus so you can rerun minimisation later
- Ask the agent to explain which oracle fits your bug class
What people use it for
- Setting up an AFL++ campaign against a file parser you own
- Writing a libFuzzer harness for a C++ function that processes untrusted input
- Building a seed corpus from a project's test suite and minimising it
- Triaging a batch of crash files into unique groups with sanitizer output
- Planning a syzkaller run against a Linux kernel subsystem in a QEMU VM
Frequently asked questions
Is the offensive-fuzzing skill free to use?
The skill is published under the MIT licence. The fuzzers and tools it references, such as AFL++, libFuzzer and syzkaller, are separate projects with their own licences, which you should check before use.
Do I need to install anything else to use this skill?
Yes. The skill is a methodology and does not include the fuzzers. You need tools like AFL++, libFuzzer through Clang, Honggfuzz, Boofuzz or syzkaller, plus CMake and sanitizers such as ASan and UBSan.
Where do I put the skill so Claude can find it?
Unzip the downloaded ZIP into ~/.claude/skills/ for personal use, or into a project's .claude/skills/ folder. You can also upload it in the Claude apps under Settings → Capabilities → Skills.
Does the skill run scripts or use the internet?
According to the skill's listing, it does not run scripts and does not use the network. The commands it describes are run by you or the agent in your own environment.
Can I use this skill to test software I do not own?
You should not. The skill is framed around attacking targets, and fuzzing without written authorisation can be disruptive or illegal. Only test systems you own or are permitted to test.
How does this compare with other fuzzing guides?
This skill is a structured playbook for an AI agent covering fuzzer choice, harnesses, corpus, campaigns and triage in one workflow. It is not a point-and-click tool, and it assumes command-line, compiler and debugger familiarity.
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Our verdict
This skill suits security researchers, developers fuzzing their own C or C++ code with sanitizers, and students learning how coverage-guided fuzzing and crash triage fit together. It is a poor fit for anyone who needs a point-and-click tool, or who wants to test systems they are not authorised to attack.
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