afl-fuzz - Man Page
Synopsis
Options
Required parameters:
-i dir - input directory with test cases (or '-' to resume, also see
AFL_AUTORESUME)
-o dir - output directory for fuzzer findings
Execution control settings:
-P strategy - set fix mutation strategy: explore (focus on new coverage),
exploit (focus on triggering crashes). You can also set a
number of seconds after without any finds it switches to
exploit mode, and back on new coverage (default: 1000)
-p schedule - power schedules compute a seed's performance score:
explore(default), fast, exploit, seek, rare, mmopt, coe, lin
quad -- see docs/FAQ.md for more information
-f file - location read by the fuzzed program (default: stdin or @@)
-t msec - timeout for each run (auto-scaled, default 1000 ms). Add a '+'
to auto-calculate the timeout, the value being the maximum.
-m megs - memory limit for child process (0 MB, 0 = no limit [default])
-O - use binary-only instrumentation (FRIDA mode)
-Q - use binary-only instrumentation (QEMU mode)
-U - use unicorn-based instrumentation (Unicorn mode)
-W - use qemu-based instrumentation with Wine (Wine mode)
-X - use VM fuzzing (NYX mode - standalone mode)
-Y - use VM fuzzing (NYX mode - multiple instances mode)
Mutator settings:
-a type - target input format, "text" or "binary" (default: generic)
-g minlength - set min length of generated fuzz input (default: 1)
-G maxlength - set max length of generated fuzz input (default: 1048576)
-L minutes - use MOpt(imize) mode and set the time limit for entering the
pacemaker mode (minutes of no new finds). 0 = immediately,
-1 = immediately and together with normal mutation.
Note: this option is usually not very effective
-u - enable testcase splicing
-c program - enable CmpLog by specifying a binary compiled for it.
if using QEMU/FRIDA or the fuzzing target is compiled
for CmpLog then use '-c 0'. To disable CMPLOG use '-c -'.
-l cmplog_opts - CmpLog configuration values (e.g. "2ATR"):
1=small files, 2=larger files (default), 3=all files,
A=arithmetic solving, T=transformational solving,
X=extreme transform solving, R=random colorization bytes.
Fuzzing behavior settings:
-Z - sequential queue selection instead of weighted random
-N - do not unlink the fuzzing input file (for devices etc.)
-n - fuzz without instrumentation (non-instrumented mode)
-x dict_file - fuzzer dictionary (see README.md, specify up to 4 times)
-w san_binary - Specify the extra sanitizer instrumented binaries,
can be specified multiple times.
Read docs/SAND.md for details.
Test settings:
-s seed - use a fixed seed for the RNG
-V seconds - fuzz for a specified time then terminate (fuzz time only!)
-E execs - fuzz for an approx. no. of total executions then terminate
Note: not precise and can have several more executions.
Other stuff:
-M/-S id - distributed mode (-M sets -Z and disables trimming)
see docs/fuzzing_in_depth.md#c-using-multiple-cores
for effective recommendations for parallel fuzzing.
-F path - sync to a foreign fuzzer queue directory (requires -M, can
be specified up to 32 times)
-z - skip the enhanced deterministic fuzzing
(note that the old -d and -D flags are ignored.)
-T text - text banner to show on the screen
-I command - execute this command/script when a new crash is found
-C - crash exploration mode (the peruvian rabbit thing)
-b cpu_id - bind the fuzzing process to the specified CPU core (0-...)
-e ext - file extension for the fuzz test input file (if needed)
Environment variables used:
LD_BIND_LAZY: do not set LD_BIND_NOW env var for target
ASAN_OPTIONS: custom settings for ASAN
(must contain abort_on_error=1 and symbolize=0)
MSAN_OPTIONS: custom settings for MSAN
(must contain exitcode=86 and symbolize=0)
AFL_AUTORESUME: resume fuzzing if directory specified by -o already exists
AFL_BENCH_JUST_ONE: run the target just once
AFL_BENCH_UNTIL_CRASH: exit soon when the first crashing input has been found
AFL_CMPLOG_ONLY_NEW: do not run cmplog on initial testcases (good for resumes!)
AFL_CRASH_EXITCODE: optional child exit code to be interpreted as crash
AFL_CUSTOM_MUTATOR_LIBRARY: lib with afl_custom_fuzz() to mutate inputs
AFL_CUSTOM_MUTATOR_ONLY: avoid AFL++'s internal mutators
AFL_CYCLE_SCHEDULES: after completing a cycle, switch to a different -p schedule
AFL_DEBUG: extra debugging output for Python mode trimming
AFL_DEBUG_CHILD: do not suppress stdout/stderr from target
AFL_DISABLE_REDUNDANT: disable any queue item that is redundant
AFL_DISABLE_TRIM: disable the trimming of test cases
AFL_DUMB_FORKSRV: use fork server without feedback from target
AFL_EXIT_WHEN_DONE: exit when all inputs are run and no new finds are found
AFL_EXIT_ON_TIME: exit when no new coverage is found within the specified time
AFL_EXIT_ON_SEED_ISSUES: exit on any kind of seed issues
AFL_EXPAND_HAVOC_NOW: immediately enable expand havoc mode (default: after 60
minutes and a cycle without finds)
AFL_FAST_CAL: limit the calibration stage to three cycles for speedup
AFL_FORCE_UI: force showing the status screen (for virtual consoles)
AFL_FORKSRV_INIT_TMOUT: time spent waiting for forkserver during startup (in ms)
AFL_HANG_TMOUT: override timeout value (in milliseconds)
AFL_I_DONT_CARE_ABOUT_MISSING_CRASHES: don't warn about core dump handlers
AFL_IGNORE_PROBLEMS: do not abort fuzzing if an incorrect setup is detected
AFL_IGNORE_PROBLEMS_COVERAGE: if set in addition to AFL_IGNORE_PROBLEMS - also
ignore those libs for coverage
AFL_IGNORE_SEED_PROBLEMS: skip over crashes and timeouts in the seeds instead of
exiting
AFL_IGNORE_TIMEOUTS: do not process or save any timeouts
AFL_IGNORE_UNKNOWN_ENVS: don't warn on unknown env vars
AFL_IMPORT_FIRST: sync and import test cases from other fuzzer instances first
AFL_INPUT_LEN_MIN/AFL_INPUT_LEN_MAX: like -g/-G set min/max fuzz length produced
AFL_PIZZA_MODE: 1 - enforce pizza mode, -1 - disable for April 1st,
0 (default) - activate on April 1st
AFL_KILL_SIGNAL: Signal ID delivered to child processes on timeout, etc.
(default: SIGKILL)
AFL_FORK_SERVER_KILL_SIGNAL: Kill signal for the fork server on termination
(default: SIGTERM). If unset and AFL_KILL_SIGNAL is
set, that value will be used.
AFL_MAP_SIZE: the shared memory size for that target. must be >= the size
the target was compiled for
AFL_MAX_DET_EXTRAS: if more entries are in the dictionary list than this value
then they are randomly selected instead all of them being
used. Defaults to 200.
AFL_NO_AFFINITY: do not check for an unused cpu core to use for fuzzing
AFL_TRY_AFFINITY: try to bind to an unused core, but don't fail if unsuccessful
AFL_NO_ARITH: skip arithmetic mutations in deterministic stage
AFL_NO_AUTODICT: do not load an offered auto dictionary compiled into a target
AFL_NO_CPU_RED: avoid red color for showing very high cpu usage
AFL_NO_FORKSRV: run target via execve instead of using the forkserver
AFL_NO_SNAPSHOT: do not use the snapshot feature (if the snapshot lkm is loaded)
AFL_NO_STARTUP_CALIBRATION: no initial seed calibration, start fuzzing at once
AFL_NO_WARN_INSTABILITY: no warn about instability issues on startup calibration
AFL_NO_UI: switch status screen off
AFL_NYX_AUX_SIZE: size of the Nyx auxiliary buffer. Must be a multiple of 4096.
Increase this value in case the crash reports are truncated.
Default value is 4096.
AFL_NYX_DISABLE_SNAPSHOT_MODE: disable snapshot mode (must be supported by the agent)
AFL_NYX_LOG: output NYX hprintf messages to another file
AFL_NYX_REUSE_SNAPSHOT: reuse an existing Nyx root snapshot
AFL_PATH: path to AFL support binaries
AFL_PYTHON_MODULE: mutate and trim inputs with the specified Python module
AFL_QUIET: suppress forkserver status messages
AFL_POST_PROCESS_KEEP_ORIGINAL: save the file as it was prior post-processing to
the queue, but execute the post-processed one
AFL_PRELOAD: LD_PRELOAD / DYLD_INSERT_LIBRARIES settings for target
AFL_TARGET_ENV: pass extra environment variables to target
AFL_SHUFFLE_QUEUE: reorder the input queue randomly on startup
AFL_SKIP_BIN_CHECK: skip afl compatibility checks, also disables auto map size
AFL_SKIP_CPUFREQ: do not warn about variable cpu clocking
AFL_STATSD: enables StatsD metrics collection
AFL_STATSD_HOST: change default statsd host (default 127.0.0.1)
AFL_STATSD_PORT: change default statsd port (default: 8125)
AFL_STATSD_TAGS_FLAVOR: set statsd tags format (default: disable tags)
supported formats: dogstatsd, librato, signalfx, influxdb
AFL_NO_FASTRESUME: do not read or write a fast resume file
AFL_NO_SYNC: disables all syncing
AFL_SYNC_TIME: sync time between fuzzing instances (in minutes)
AFL_FINAL_SYNC: sync a final time when exiting (will delay the exit!)
AFL_NO_CRASH_README: do not create a README in the crashes directory
AFL_TESTCACHE_SIZE: use a cache for testcases, improves performance (in MB)
AFL_TMPDIR: directory to use for input file generation (ramdisk recommended)
AFL_EARLY_FORKSERVER: force an early forkserver in an afl-clang-fast/
afl-clang-lto/afl-gcc-fast target
AFL_PERSISTENT: enforce persistent mode (if __AFL_LOOP is in a shared lib)
AFL_DEFER_FORKSRV: enforced deferred forkserver (__AFL_INIT is in a shared lib)
AFL_FUZZER_STATS_UPDATE_INTERVAL: interval to update fuzzer_stats file in
seconds (default: 60, minimum: 1)
Compiled without Python module support.
Compiled without AFL_PERSISTENT_RECORD support.
Compiled with shmat support.
For additional help please consult docs/README.md :)Author
AFL++ was written by Michal "lcamtuf" Zalewski and is maintained by Marc "van Hauser" Heuse <mh@mh-sec.de>, Dominik Maier <domenukk@gmail.com>, Andrea Fioraldi <andreafioraldi@gmail.com> and Heiko "hexcoder-" Eissfeldt <heiko.eissfeldt@hexco.de> The homepage of AFL++ is: https://github.com/AFLplusplus/AFLplusplus
License
Apache License Version 2.0, January 2004
Info
2025-10-01 AFL++