Performing Fuzzing with AFL++

---
name: performing-fuzzing-with-aflplusplus-970e2f4ea464
description: 'Performs coverage-guided fuzzing of compiled binaries with AFL++, instrumenting
  targets via afl-cc/afl-clang-fast, minimizing corpora with afl-cmin and afl-tmin,
  running parallel campaigns with afl-fuzz, and triaging crashes with CASR or GDB
  scripts. Use for binary fuzzing, crash and memory-corruption discovery, coverage-guided
  testing, or running AFL++ fuzzing campaigns.

  '
domain: cybersecurity
subdomain: application-security
tags:
- fuzzing
- aflplusplus
- coverage-guided
- crash-triage
- binary-analysis
- security-testing
version: '1.0'
author: mahipal
license: Apache-2.0
nist_ai_rmf:
- MEASURE-2.7
- MAP-5.1
- MANAGE-2.4
atlas_techniques:
- AML.T0070
- AML.T0066
- AML.T0082
nist_csf:
- PR.PS-01
- PR.PS-04
- ID.RA-01
- PR.DS-10
mitre_attack:
- T1078
- T1190
- T1059
- T1005
---
# Performing Fuzzing with AFL++

## Overview

AFL++ is a community-maintained fork of American Fuzzy Lop (AFL) that provides coverage-guided
fuzzing for compiled binaries. It instruments targets at compile time or via QEMU/Unicorn mode
for binary-only fuzzing, then mutates input corpora to discover new code paths. AFL++ includes
advanced scheduling (MOpt, rare), custom mutators, CMPLOG for input-to-state comparison solving,
and persistent mode for high-throughput fuzzing.


## When to Use

- When conducting security assessments that involve performing fuzzing with aflplusplus
- When following incident response procedures for related security events
- When performing scheduled security testing or auditing activities
- When validating security controls through hands-on testing

## Prerequisites

- AFL++ installed (`apt install afl++` or build from source)
- Target binary source code (for compile-time instrumentation) or QEMU mode for binary-only
- Initial seed corpus of valid inputs for the target format
- Linux system with /proc/sys/kernel/core_pattern configured

## Steps

1. Instrument the target binary with `afl-cc` or `afl-clang-fast`
2. Prepare seed corpus directory with minimal valid inputs
3. Minimize corpus with `afl-cmin` to remove redundant seeds
4. Run `afl-fuzz` with appropriate flags (-i input -o output)
5. Monitor fuzzing progress via afl-whatsup and UI stats
6. Triage crashes with `afl-tmin` minimization and CASR/GDB analysis
7. Report unique crashes with reproduction steps

## Expected Output

```
+++ Findings +++
  unique crashes: 12
  unique hangs: 3
  last crash: 00:02:15 ago
+++ Coverage +++
  map density: 4.23% / 8.41%
  paths found: 1847
  exec speed: 2145/sec
```