cfuzz

Why?
To perform fuzzing or bruteforcing we have plenty of awesome tools (fuff and wfuzz for web fuzzing, hydra for network bruteforcing, to mention just a few). cfuzz is a tool that propose a different approach with a step-back. The aim is to be able to fuzz/bruteforce anything that can be transcribed in command line.

Consequently, cfuzz can be seen either as an alternative of these tools for simple use case or an extension cause it handles a huge range of use cases

_{Origins of the idea: when bruteforcing ipmi service to enumerate users. 3 options: use msfconsole, write module for hydra, manually or programmaticaly parse ipmitool tool output}

Demo

Install

From release:

curl -lO -L -s https://github.com/ariary/cfuzz/releases/latest/download/cfuzz && chmod +x cfuzz

With go:

go install github.com/ariary/cfuzz/cmd/cfuzz@latest

Usage

Indicate:

• the command, with the fuzzing part determined with the keyword FUZZ
• the wordlist

and let's get it!

export CFUZZ_CMD="printf FUZZ | sudo -S id" # Example bruteforcing user password, I haven't found better
cfuzz -w [wordlist] 

Or if you prefer in one line:

# example for subdomain enum
cfuzz -w [wordlist] ping -c 4 FUZZ.domain.net

Additionnaly it is possible to:

• Filter results
• Custom displayed field
• Configure cfuzz run
• Generate wordlists with AI
• Use cfuzz as an MCP server

Filter results

Additionaly, it is possible to filter displayed results:

stdout filters:

  --stdout-min n      show only if stdout character count >= n
  --stdout-max n      show only if stdout character count <= n
  --stdout-eq  n      show only if stdout character count == n
  --stdout-word w     show only if stdout contains word w (repeatable)

stderr filters:

  --stderr-min n      show only if stderr character count >= n
  --stderr-max n      show only if stderr character count <= n
  --stderr-eq  n      show only if stderr character count == n
  --stderr-word w     show only if stderr contains word w (repeatable)

execution time filters:

  --time-min n        show only if execution time >= n seconds
  --time-max n        show only if execution time <= n seconds
  --time-eq  n        show only if execution time == n seconds

command exit code filters:

  --success           show only if execution returns exit code 0
  --failure           show only if execution returns a non-zero exit code

To only display results that don't pass the filter use -H or --hide flag.

cfuzz run configuration

To make cfuzz more flexible and adapt to different constraints, many options are possible:

  -w, --wordlist        wordlist file(s) for fuzzing (repeatable with --spider)
  -d, --delay           delay in ms between goroutine launches (default: 0)
  -j, --threads         max concurrent workers (default: 50)
  -k, --keyword         keyword to replace in command (default: FUZZ)
  -s, --shell           shell to use for execution (default: /bin/bash)
      --timeout         command execution timeout in seconds (default: 30)
  -i, --input           provide command stdin
      --stdin-fuzzing   fuzz stdin instead of command line
  -m, --spider          fuzz multiple keyword positions (requires multiple -w)
      --stdin-wordlist  read wordlist from cfuzz stdin

Displayed field

It is also possible to choose which result field is displayed in cfuzz output (also possible to use several):

      --stdout-chars    display stdout character count
      --stderr-chars    display stderr character count
  -t, --time            display execution time
  -c, --code            display exit code
      --no-banner       hide banner
  -r, --only-word       print only matched words (no metadata columns)
  -f, --full-output     display full command execution output (can't be combined with other display modes)

AI features

cfuzz integrates with Claude (via the Anthropic API) for two AI-powered workflows. Both require the ANTHROPIC_API_KEY environment variable to be set.

AI filter — describe what an interesting result looks like in plain English; cfuzz will ask Claude to evaluate each execution result and only show the ones that match:

cfuzz -w wordlist.txt --ai-filter "output contains an error about invalid credentials" \
  curl -s http://target/login -d "user=admin&pass=FUZZ"

AI wordlist generation — generate a context-aware wordlist by describing what you need:

cfuzz wordlist "default credentials for network switches"
cfuzz wordlist "common web admin paths" -n 50

Output is printed to stdout, one entry per line, making it easy to pipe directly into cfuzz:

cfuzz wordlist "linux privilege escalation binaries" | \
  cfuzz --stdin-wordlist "sudo -l FUZZ 2>/dev/null | grep -v 'not allowed'"

MCP server

cfuzz can run as a Model Context Protocol server, exposing a fuzz tool that any MCP-compatible AI assistant can call:

cfuzz mcp

To register with Claude Desktop, add to ~/.claude/claude_desktop_config.json:

{
  "mcpServers": {
    "cfuzz": { "command": "cfuzz", "args": ["mcp"] }
  }
}

The fuzz tool accepts: command (string), wordlist (array of strings), and optional threads, timeout, success_only, stdout_word, and ai_filter parameters.