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libafl

Build custom Rust-based fuzzers using LibAFL's modular fuzzing library components.

Updated Mar 22, 2026
Search Tags:#security testing#rust#coverage#fuzzing#fuzzer#sanitizer#libafl
One-click install
npx skills add https://github.com/TECH-HY/SKILLS --skill libafl-tech-hy
Or copy as Structured Prompt for Agent▼
Please help me install this Agent Skill.
Skill: libafl
Source: https://github.com/TECH-HY/SKILLS/tree/main/skills/libafl
Command: npx skills add https://github.com/TECH-HY/SKILLS --skill libafl-tech-hy

SYSTEM DOCUMENTATION & REQUIREMENTS

What problem does it solve? Standard fuzzers like libFuzzer and AFL++ lack support for custom mutation strategies, non-standard target architectures, and novel fuzzing research techniques. This Skill guides you through building fully customized fuzzers with LibAFL's modular Rust components. ## Core Features & Use Cases - libFuzzer Drop-in Replacement: Reuse existing libFuzzer harnesses with LibAFL's compatibility runtime for improved multi-core fuzzing. - Custom Fuzzer Construction: Assemble observers, feedback, objectives, mutators, schedulers, and executors into a tailored fuzzer as a Rust library. - Advanced Techniques: Configure crash deduplication via backtrace hashing, dictionary and auto-token fuzzing, multi-core campaigns, and compiler wrappers for automatic instrumentation. - Use Case: Fuzz libpng by building it with the LibAFL compiler wrapper, linking the OSS-Fuzz harness, seeding with a PNG corpus and dictionary, then launching a multi-core campaign. ## Quick Start Ask the AI to set up a LibAFL fuzzer for your C/C++ target, including the compiler wrapper, harness, seed corpus, and a multi-core fuzzing command.

Frequently Asked Questions about libafl

High-intent search queries and answers about installing and using this skill.

FAQPage Schema
How do I build a custom fuzzer with LibAFL?▼

Create a Rust library project with libafl, libafl_targets, libafl_bolts, and libafl_cc dependencies, then assemble observers, feedback, objectives, a mutator, scheduler, and executor around your harness. Launch it with the Launcher builder across selected cores.

LibAFL vs libFuzzer vs AFL++: which fuzzer should I use?▼

libFuzzer suits quick single-threaded setups, AFL++ fits general multi-core fuzzing, and LibAFL is best when you need custom mutation strategies, fine-grained component control, or fuzzing research capabilities.

Can LibAFL run existing libFuzzer harnesses?▼

Yes, LibAFL provides a libFuzzer compatibility runtime built from the libafl_libfuzzer_runtime directory. Compile your existing LLVMFuzzerTestOneInput harness against the produced libFuzzer.a and run it as a drop-in replacement.

What LLVM version does LibAFL require?▼

LibAFL requires Clang/LLVM versions 15 through 18. Set RUSTFLAGS, CC, and CXX to point at the matching clang binaries, and install nightly Rust with llvm-tools for libFuzzer compatibility mode.

Why does my LibAFL fuzzer show no coverage increase?▼

Missing coverage usually means instrumentation failed during compilation. Verify the LibAFL compiler wrapper was used and that -fsanitize-coverage=trace-pc-guard flags were applied when building the target.

How do I avoid duplicate crashes in LibAFL?▼

Add a BacktraceObserver to the executor and combine CrashFeedback with NewHashFeedback in the objective. This stores only crashes with unique backtraces, deduplicating repeated findings from the same bug.

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