Overview

Nuclei is a fast, template-based vulnerability scanner by ProjectDiscovery. Instead of running monolithic scanners, Nuclei uses YAML templates — each one checks for a specific vulnerability, misconfiguration, or exposure. Community maintains 8000+ templates covering CVEs, default credentials, exposed panels, misconfigurations, and more. Runs in CI, scripted pipelines, or manual assessments.

When to Use

Security assessment of web applications before deployment
Checking infrastructure for known CVEs and misconfigurations
Continuous security scanning in CI/CD pipelines
Bug bounty reconnaissance and vulnerability discovery
Compliance checks (exposed admin panels, default credentials, SSL issues)

Instructions

Setup

bash

# Install via Go
go install -v github.com/projectdiscovery/nuclei/v3/cmd/nuclei@latest

# Or download binary
curl -sL https://github.com/projectdiscovery/nuclei/releases/latest/download/nuclei_linux_amd64.zip -o nuclei.zip
unzip nuclei.zip

# Update templates (8000+ community templates)
nuclei -update-templates

Basic Scanning

bash

# Scan a single target with all templates
nuclei -u https://example.com

# Scan with specific severity
nuclei -u https://example.com -severity critical,high

# Scan multiple targets from a file
nuclei -l targets.txt -severity critical,high,medium

# Scan specific template categories
nuclei -u https://example.com -tags cve,misconfig,exposure

# Scan with rate limiting (respectful scanning)
nuclei -u https://example.com -rate-limit 50 -concurrency 10

Custom Templates

yaml

# templates/exposed-env.yaml — Check for exposed .env files
id: exposed-env-file

info:
  name: Exposed .env File
  author: terminal-skills
  severity: high
  description: Checks if .env file is publicly accessible
  tags: misconfig,exposure

http:
  - method: GET
    path:
      - "{{BaseURL}}/.env"
    matchers-condition: and
    matchers:
      - type: word
        words:
          - "DB_PASSWORD"
          - "API_KEY"
          - "SECRET"
        condition: or
      - type: status
        status:
          - 200

yaml

# templates/api-key-leak.yaml — Detect API keys in responses
id: api-key-in-response

info:
  name: API Key Leaked in Response
  author: terminal-skills
  severity: medium
  tags: exposure,api

http:
  - method: GET
    path:
      - "{{BaseURL}}/api/config"
      - "{{BaseURL}}/api/settings"
      - "{{BaseURL}}/config.json"
    matchers:
      - type: regex
        regex:
          - "sk_live_[a-zA-Z0-9]{24}"     # Stripe live key
          - "AKIA[0-9A-Z]{16}"            # AWS access key
          - "ghp_[a-zA-Z0-9]{36}"         # GitHub token
    extractors:
      - type: regex
        regex:
          - "sk_live_[a-zA-Z0-9]{24}"
          - "AKIA[0-9A-Z]{16}"

CI/CD Integration

yaml

# .github/workflows/security-scan.yml
name: Security Scan
on:
  schedule:
    - cron: "0 6 * * 1"  # Weekly Monday 6 AM
  workflow_dispatch:

jobs:
  nuclei-scan:
    runs-on: ubuntu-latest
    steps:
      - uses: projectdiscovery/nuclei-action@main
        with:
          target: https://myapp.com
          flags: "-severity critical,high -tags cve,misconfig"
          output: nuclei-report.txt

      - name: Alert on findings
        if: success()
        run: |
          if [ -s nuclei-report.txt ]; then
            echo "⚠️ Vulnerabilities found!"
            cat nuclei-report.txt
            # Send to Slack/email
          fi

Programmatic Usage (Go/Python)

python

# scan.py — Run Nuclei from Python and parse results
import subprocess
import json

def run_nuclei_scan(target: str, severity: str = "critical,high") -> list[dict]:
    """Run Nuclei scan and return structured results."""
    result = subprocess.run(
        ["nuclei", "-u", target, "-severity", severity, "-json", "-silent"],
        capture_output=True, text=True,
    )

    findings = []
    for line in result.stdout.strip().split("\n"):
        if line:
            findings.append(json.loads(line))

    return findings

# Usage
findings = run_nuclei_scan("https://example.com")
for f in findings:
    print(f"[{f['info']['severity']}] {f['info']['name']} — {f['matched-at']}")

Examples

Example 1: Pre-deployment security check

User prompt: "Before we go live, scan our staging site for any critical vulnerabilities or misconfigurations."

The agent will run Nuclei with critical/high severity templates, check for exposed files, default credentials, known CVEs, and generate a report with remediation steps.

Example 2: Custom template for internal API

User prompt: "Write a Nuclei template that checks if our internal admin endpoints are accessible without auth."

The agent will create a YAML template that hits admin endpoints, checks for 200 status without auth headers, and flags exposed admin panels.

Guidelines

Always get authorization — only scan targets you own or have written permission to test
Start with -severity critical,high — focus on what matters first
Rate limit scans — -rate-limit 50 to avoid overwhelming targets
Use -tags for targeted scans — cve, misconfig, exposure, default-login
JSON output for automation — -json flag for parseable results
Custom templates for your app — community templates are generic; write app-specific checks
Update templates regularly — nuclei -update-templates gets new CVE checks
Headless templates for JS apps — some checks require browser rendering
Never scan production during peak hours — schedule scans for low-traffic windows

nuclei-scanner

Usage

Getting Started

Example Prompts

Documentation

Overview

When to Use

Instructions

Setup

Basic Scanning

Custom Templates

CI/CD Integration

Programmatic Usage (Go/Python)

Examples

Example 1: Pre-deployment security check

Example 2: Custom template for internal API

Guidelines

Information

Use Cases