atheris

Fuzz Python code and C extensions with libFuzzer and AddressSanitizer.

Updated Nov 23, 2025
One-click install
npx skills add https://github.com/manuelbrandner85/Weltenbibliothekapp --skill atheris-manuelbrandner85
Or copy as Structured Prompt for Agent
Please help me install this Agent Skill.
Skill: atheris
Source: https://github.com/manuelbrandner85/Weltenbibliothekapp/tree/main/.agents/skills/atheris
Command: npx skills add https://github.com/manuelbrandner85/Weltenbibliothekapp --skill atheris-manuelbrandner85

SYSTEM DOCUMENTATION & REQUIREMENTS

What problem does it solve?

Atheris identifies elusive memory corruption bugs and crashes in Python code and C extensions that traditional unit testing often misses.

Core Features & Use Cases

  • Coverage-Guided Fuzzing: Uses libFuzzer to intelligently explore code paths and maximize test coverage.
  • Memory Safety: Integrates with AddressSanitizer (ASan) to detect memory leaks and buffer overflows in C extensions.
  • Use Case: Use this tool to stress-test a custom Python C extension for image processing to ensure it handles malformed input without crashing or leaking memory.

Quick Start

Use the atheris skill to fuzz the target function in your python script by running the fuzzer with your defined input harness.

Frequently Asked Questions about atheris

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

FAQPage Schema
How do I use coverage-guided fuzzing to find memory corruption in Python C extensions?

Coverage-guided fuzzing detects memory corruption in Python C extensions by using libFuzzer to explore code paths and integrating AddressSanitizer to identify memory leaks and buffer overflows. You define an input harness to stress-test target functions.

What is coverage-guided fuzzing used for in Python testing?

Coverage-guided fuzzing is used in Python testing to intelligently explore code paths and maximize test coverage, identifying elusive runtime crashes and memory corruption bugs that traditional unit testing often misses.

Do I need clang and AddressSanitizer to fuzz Python code for memory safety?

Yes, you need a configured environment with clang and appropriate sanitizer flags to fuzz Python code accurately. AddressSanitizer integration is required to detect memory leaks and buffer overflows in native C extensions.

What is the best way to detect buffer overflows when fuzzing C extensions?

The best way to detect buffer overflows when fuzzing C extensions is integrating AddressSanitizer with libFuzzer. This combination performs deep code path exploration to accurately expose memory safety issues and runtime crashes.

How do I set up an input harness for fuzzing a Python script?

To set up an input harness for fuzzing a Python script, define a target function that processes generated inputs, then run the fuzzer to stress-test it. This exposes memory corruption and crashes from malformed input.

Why does traditional unit testing miss memory corruption bugs in Python?

Traditional unit testing misses memory corruption bugs in Python because it lacks coverage-guided code path exploration. Fuzzing with libFuzzer intelligently generates inputs to trigger elusive memory leaks and buffer overflows in C extensions.