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
- Instrument the target binary with
afl-cc or afl-clang-fast
- Prepare seed corpus directory with minimal valid inputs
- Minimize corpus with
afl-cmin to remove redundant seeds
- Run
afl-fuzz with appropriate flags (-i input -o output)
- Monitor fuzzing progress via afl-whatsup and UI stats
- Triage crashes with
afl-tmin minimization and CASR/GDB analysis
- 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
---
name: performing-fuzzing-with-aflplusplus
description: Perform coverage-guided fuzzing of compiled binaries using AFL++ to discover memory corruption, crashes, and security vulnerabilities.
license: Apache-2.0
---
# 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
```
