tinyfuzz

Minimal protocol fuzzing framework for quickly testing networked services and parsers.

Usage

# Fuzz a TCP service
python tinyfuzz.py "GET / HTTP/1.0\r\n\r\n" tcp localhost 8080

# Fuzz a UDP service
python tinyfuzz.py "ping" udp localhost 9999 --timeout 2.0

# Fuzz a local binary via stdin
python tinyfuzz.py "hello" proc ./target_binary

# Use a binary seed file
python tinyfuzz.py @seed.bin tcp localhost 8080

# Reproducible run
python tinyfuzz.py "hello" tcp localhost 8080 --seed-val 42 -n 500

Options

Flag	Default	Description
-n	1000	Number of iterations
-d	0.0	Delay between sends (seconds)
--timeout	3.0	Socket timeout (tcp/udp)
--seed-val	—	RNG seed for reproducibility

Mutation strategies

• Bit flip — flips a random bit in the payload
• Byte random — replaces a random byte with a random value
• Boundary — replaces payload with a known-dangerous value
• Repeat — repeats a chunk of the payload many times
• Truncate — shortens the payload

Crash detection

• TCP/UDP: connection refused, timeout, or socket error
• Proc: non-zero exit code (excluding 0 and 1)