🛡️ API Fuzzer Toolkit

A flexible and customizable CLI tool to fuzz API endpoints based on Swagger/OpenAPI specifications. Supports advanced modes like combo fuzzing, HTML reporting, regex-based response filtering, and proxy integration.

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🔧 Features

• Fuzz REST APIs using wordlists with <<FUZZ_param>> placeholders
• Swagger/OpenAPI support with interactive param selection
• Combo Mode (Cluster Bomb style multi-param fuzzing)
• HTML report generation (side-by-side request/response)
• Regex-based filtering on response body (case-insensitive)
• Proxy support for routing traffic through tools like Burp Suite / mitmproxy
• Auth header injection (--auth-header)
• Optional request/response logging
• Baseline response comparison
• Static-only mode (no fuzzing) if no parameters selected

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🚀 Getting Started

1. Clone the Repo

git clone https://github.com/pullkitsan/api-fuzzer.git
cd api-fuzzer

2. Install Dependencies

Install Python dependencies with:

pip install -r requirements.txt

3. Run the Tool

Swagger-based Interactive Flow

python api_fuzzer.py --swagger-file openapi.json --base-url http://localhost:5000

Dry run - Shows the parsed endpoints from api spec file

python api_fuzzer.py --swagger-file openapi.json --base-url http://localhost:5000 --dry-run

CLI Manual Mode

python api_fuzzer.py \
  --url 'http://localhost:5000/api/users/userId' \
  --method POST \
  --body '{"username": "<<FUZZ_username>>", "email": “<<FUZZ_email>>”}' \
  --params username,email \
  --combo \
  --wordlist list.txt \
  --proxy http://127.0.0.1:8080 \
  --report report.html

CLI Manual Mode with Custom Headers

python api_fuzzer.py \
  --url 'http://localhost:5000/api/users/userId' \
  --method POST \
  --body '{"username": "<<FUZZ_username>>", "email": “<<FUZZ_email>>”}' \
  --params username,email \
  --combo \
  --wordlist list.txt \
  --headers '{"Authorization": "Bearer abc123", "X-Env": "staging"}' \
  --proxy http://127.0.0.1:8080 \
  --report report.html

CLI Swagger Mode

python api_fuzzer.py \
  --base-url http://localhost:5000 \
  --swagger-file <API_SPEC_FILE> \
  --report <REPORT_NAME> \
  --proxy http://127.0.0.1:8080 \
  --combo

📄 Arguments

Argument	Description
--swagger-file	Path to Swagger/OpenAPI JSON
--base-url	Base URL to prefix all endpoints( used with api spec file)
--url	Full URL (manual mode and not used with api spec file)
--method	HTTP method (GET, POST, PUT...)
--body	Request body with <<FUZZ_param>> placeholders
--params	Comma-separated list of params to fuzz
--wordlist	Wordlist path
--combo	Enable combo mode
--delay	Delay between requests
--auth-header	Authorization header
--proxy	HTTP/HTTPS proxy (e.g., Burp Suite)
--include-regex	Case-insensitive regex to match response body
--save-request	Save all requests to file( results/requests.txt )
--save-response	Save all responses to file ( results/responses.txt)
--report	Generate HTML report
--dry-run	Shows parsed api endpoints with parameters to fuzz
--help	Displays all the available arguments

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📦 Requirements

Install dependencies via:

pip install -r requirements.txt

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📊 Report Example

The tool generates a clean HTML report that shows:

• Request URL, headers, and body on the left
• Response headers and body on the right
• Color-coded status and lengths
• Only interesting or filtered responses (if regex is used)

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GUI mode

python api_fuzzer_gui.py 

Video.mov

✅ TODO / Roadmap

• Proxy routing
• Swagger integration
• Auth header support
• HTML report generation
• Combo fuzzing
• Regex filter
• gRPC support
• Learning mode from proxied traffic

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