Vulnerability Analysisfuzzerblack-boxtestingnetworkprotocol

sfuzz

sfuzz is a simple black box testing utility for fuzzing network services and protocols. It provides a flexible framework for generating and sending fuzz data to remote hosts.

Description

sfuzz, or Simple Fuzzer, is designed as an easy-to-use black box testing suite similar to the Generic Protocol Framework. Its primary goal is to offer a powerful yet straightforward tool for fuzzing to identify vulnerabilities in network services without requiring deep knowledge of the internal protocol structures.

Use cases include testing HTTP servers, custom protocols, or any TCP/UDP service by supplying a configuration file that defines fuzzing points. It supports literal and sequence fuzzing modes, logging, and integration with monitoring tools like sfo for crash detection.

The tool is particularly suited for penetration testers needing quick setup for protocol fuzzing in controlled environments.

How It Works

sfuzz reads a configuration file (e.g., basic.http) that specifies fuzzing points with literals, sequences, and symbols. It generates mutated payloads based on these definitions and sends them over TCP, UDP, or to output. Options like state, lineno, req_del, and mseq_len control fuzzing progression and timing. It integrates with sfo for spawning monitored oracle processes to detect crashes via exit statuses.

Installation

bash
sudo apt install sfuzz

Flags

-hThis message.
-VVersion information.
-vVerbose output
-qSilent output mode (generally for CLI fuzzing)
-Xprints the output in hex
-bBegin fuzzing at the test specified.
-eEnd testing on failure.
-tWait time for reading the socket
-SRemote host
-pPort
-T|-U|-OTCP|UDP|Output mode
-RRefrain from closing connections (ie: "leak" them)
-fConfig File
-LLog file
-nCreate a new logfile after each fuzz
-rTrim the tailing newline
-DDefine a symbol and value (X=y).
-lOnly perform literal fuzzing
-sOnly perform sequence fuzzing

Examples

Fuzz the target server on port 10443 with TCP output mode using the basic HTTP config.
sfuzz -S 192.168.1.1 -p 10443 -T -f /usr/share/sfuzz/sfuzz-sample/basic.http
Display the help message and list all available flags.
sfuzz -h
Show help for sfo, the oracle monitor used with sfuzz for crash detection.
sfo -h
Display version information for sfuzz.
sfuzz -V
Fuzz a target with verbose output using a custom config file.
sfuzz -S 192.168.1.1 -p 10443 -T -f config.http -v
Fuzz HTTP on port 80 and log output to a file.
sfuzz -S target.host -p 80 -T -f /usr/share/sfuzz/sfuzz-sample/basic.http -L fuzz.log
Updated 2026-04-16kali.org ↗