Cloudflare Security Audit Skill

cloudflare-security-audit-skill

Skill by ara.so — Security Skills collection.

A coding-agent skill that orchestrates multi-phase security audits through parallel agents. It runs six phases: reconnaissance, hunting, adversarial validation, reporting, structured output generation, and independent verification. Designed to find exploitable vulnerabilities with real impact, not theoretical issues.

This is the open-source skill that seeded Cloudflare's vulnerability discovery harness. Multiple runs against the same codebase are additive—each explores different attack surfaces while reading prior findings to avoid duplicates.

What it does

The skill coordinates multiple parallel agents through a structured pipeline:

1. Recon — Maps architecture, trust boundaries, input surfaces → architecture.md
2. Hunt — 7 parallel agents attack from different angles (injection, access control, business logic, crypto, feature abuse, chained attacks, wildcard)
3. Validate — Separate agents adversarially review each finding to eliminate false positives
4. Report — Generates REPORT.md and FINDINGS-DETAIL.md
5. Structured output — Produces findings.json validated against report-schema.json
6. Independent verification — Fresh agents verify every claim against actual source code

Installation

Install using the Skills CLI:

npx skills add https://github.com/cloudflare/security-audit-skill \
  --skill security-audit

For user-level installation (available across all projects):

npx skills add https://github.com/cloudflare/security-audit-skill \
  --skill security-audit \
  --global

Check installation:

npx skills list

Usage

Basic audit

Navigate to the codebase you want to audit and invoke:

security audit this codebase

find security vulnerabilities in ./src

do a security review

The skill activates on trigger phrases and prompts for an output directory if not specified.

Specify output directory

security audit this project, output to ~/audits/myapp

run security-audit skill on ./api, save to /tmp/audit-results

Default output location: ~/security-audit-skill/<repo-name>/run-<N>

Target specific directories

audit the authentication module in ./src/auth

find vulnerabilities in ./payment-processing

Multi-run strategy

Run multiple audits for better coverage (each explores different paths):

security audit this codebase (run 1 of 3)

The skill reads prior findings.json files to skip known issues and target unexplored areas.

Core principles

The skill enforces strict security research standards:

Only report exploitable findings

Every finding requires:

• Concrete attack scenario
• Actual input/payload
• Observable impact
• Not "could theoretically" or "might allow"

Good: "CSRF in /api/delete-account — no token validation. POST from attacker.com deletes victim's account."

Bad: "Endpoint lacks CSRF protection and could be vulnerable."

Adversarial validation

• The validator agent is never the finder agent
• Validators attempt to disprove findings
• Findings survive only if exploitation path is reproducible

Severity = Likelihood × Impact

Not "deviates from best practice" but actual risk:

• CRITICAL: Full system compromise, data exfiltration, RCE
• HIGH: Authentication bypass, privilege escalation, PII leak
• MEDIUM: Partial data exposure, limited privilege escalation
• LOW: Information disclosure with minimal impact
• INFO: Defense-in-depth gaps, hardening opportunities

Defense-in-depth gaps ≠ vulnerabilities

If Layer A blocks the attack, missing Layer B is a hardening note, not a vulnerability.

Example: If input validation prevents SQL injection, missing prepared statements is INFO at best.

Output files

After a complete audit run, the output directory contains:

Schema validation

The skill includes zero-dependency validation:

// validate-findings.cjs usage
const { validateFindings } = require('./validate-findings.cjs');
const findings = require('./findings.json');

const result = validateFindings(findings);
if (!result.valid) {
  console.error('Validation errors:', result.errors);
  process.exit(1);
}

Run standalone validation:

node validate-findings.cjs path/to/findings.json

findings.json structure

{
  "audit_metadata": {
    "audit_date": "2026-06-20T10:30:00Z",
    "target_repository": "acme/payments-api",
    "skill_version": "1.0.0",
    "run_number": 1
  },
  "confirmed_findings": [
    {
      "id": "VULN-001",
      "title": "SQL Injection in transaction search",
      "severity": "CRITICAL",
      "category": "Injection",
      "description": "User-supplied 'query' parameter concatenated directly into SQL",
      "location": {
        "file": "src/transactions.js",
        "line_start": 45,
        "line_end": 48,
        "function": "searchTransactions"
      },
      "exploit_scenario": {
        "attack_vector": "GET /api/transactions?query=' OR '1'='1",
        "preconditions": ["Authenticated user"],
        "impact": "Full database read access, including other users' transactions"
      },
      "evidence": {
        "vulnerable_code": "const sql = `SELECT * FROM transactions WHERE description LIKE '%${req.query.query}%'`;",
        "proof_of_concept": "curl -H 'Authorization: Bearer $TOKEN' 'https://api.example.com/api/transactions?query=%27%20OR%20%271%27=%271'"
      },
      "remediation": "Use parameterized queries: `SELECT * FROM transactions WHERE description LIKE ?` with bound parameter",
      "cwe_ids": ["CWE-89"],
      "verification_status": "independently_verified",
      "verification_notes": "Confirmed vulnerable code at src/transactions.js:45-48. No input sanitization present."
    }
  ],
  "rejected_findings": [
    {
      "id": "REJECT-001",
      "title": "Missing rate limiting on login endpoint",
      "reason": "WAF-level rate limiting confirmed in infrastructure layer (cloudflare-config.yaml). Defense-in-depth gap, not exploitable vulnerability.",
      "rejected_by": "validator-agent-3",
      "original_severity": "MEDIUM"
    }
  ],
  "coverage_notes": "Focused on API layer (./src/api). Database layer (./src/db) deferred to next run.",
  "prior_runs_reviewed": ["run-1/findings.json"]
}

Attack classes

The hunting phase spawns parallel agents for:

Core attack classes

1. Injection — SQL, NoSQL, command, template, XSS, XXE
2. Access Control — Broken auth, IDOR, privilege escalation, path traversal
3. Business Logic — Race conditions, state manipulation, workflow bypass
4. Cryptography — Weak crypto, key management, random number generation
5. Feature Abuse — Intended features used maliciously
6. Chained Attacks — Multi-step exploitation chains

Wildcard agent

Explores unconventional attack surfaces specific to the codebase's domain.

Obvious-things sweep

Quick pass for common mistakes (hardcoded secrets, debug endpoints, default credentials).

Configuration

The skill reads configuration from:

1. Command-line flags (via Skills CLI)
2. Skill metadata in the repository (.skills/security-audit.json)
3. Environment variables

Environment variables

# Output directory override
export SECURITY_AUDIT_OUTPUT_DIR=~/custom-audits

# Parallel agent count (default: 7 for hunting phase)
export SECURITY_AUDIT_PARALLEL_AGENTS=10

# Skip phases (comma-separated: recon,hunt,validate,report,structured,verify)
export SECURITY_AUDIT_SKIP_PHASES=recon

# Minimum severity to report (CRITICAL, HIGH, MEDIUM, LOW, INFO)
export SECURITY_AUDIT_MIN_SEVERITY=MEDIUM

# Read prior runs from custom location
export SECURITY_AUDIT_PRIOR_RUNS_DIR=~/audits/myapp

Per-project configuration

Create .skills/security-audit.json in your repository:

{
  "exclude_paths": [
    "test/**",
    "node_modules/**",
    "vendor/**"
  ],
  "focus_areas": [
    "src/auth",
    "src/payment"
  ],
  "custom_attack_classes": [
    {
      "name": "GraphQL-specific",
      "description": "Query complexity attacks, introspection abuse, batching vulnerabilities"
    }
  ],
  "severity_overrides": {
    "info_to_low": ["Missing security headers on non-sensitive endpoints"]
  }
}

Common patterns

Pattern: Incremental coverage

Run multiple audits with different focus areas:

# Run 1: Authentication
security audit ./src/auth, output to ~/audits/myapp/run-1

# Run 2: API layer (reads run-1 findings)
security audit ./src/api, output to ~/audits/myapp/run-2

# Run 3: Business logic (reads run-1 and run-2)
security audit ./src/services, output to ~/audits/myapp/run-3

Pattern: CI/CD integration

# .github/workflows/security-audit.yml
name: Security Audit
on:
  schedule:
    - cron: '0 0 * * 0'  # Weekly
  workflow_dispatch:

jobs:
  audit:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v4
      - uses: actions/setup-node@v4
      
      - name: Install skill
        run: npx skills add https://github.com/cloudflare/security-audit-skill --skill security-audit
      
      - name: Run audit
        run: |
          # Your coding agent invocation here
          # Example with Claude Code (adjust for your agent)
          echo "security audit this codebase, output to ./audit-results" | your-agent-cli
      
      - name: Upload results
        uses: actions/upload-artifact@v4
        with:
          name: security-audit
          path: audit-results/
      
      - name: Check for critical findings
        run: |
          node -e "
            const findings = require('./audit-results/findings.json');
            const critical = findings.confirmed_findings.filter(f => f.severity === 'CRITICAL');
            if (critical.length > 0) {
              console.error(\`Found \${critical.length} CRITICAL findings\`);
              process.exit(1);
            }
          "

Pattern: Custom attack class

Extend hunting with domain-specific attacks:

// .skills/custom-attacks/api-gateway-abuse.md

# API Gateway Abuse Attack Class

## Objective
Find vulnerabilities in API gateway routing, transformation, and authentication delegation.

## Attack vectors

1. **Path manipulation**
   - Backend routing confusion via path traversal
   - Host header injection to backend services
   - HTTP method override bypass

2. **Transformation vulnerabilities**
   - JSON-to-XML conversion XXE
   - Query parameter injection via transformation
   - Header smuggling through gateway rewrites

3. **Auth delegation issues**
   - JWT validation in gateway but not backend
   - API key leakage in error messages
   - Rate limit bypass via different endpoints

## Success criteria
- Concrete request/response showing bypass
- Backend behavior different from gateway expectations
- Actual impact (data access, privilege escalation)

Then reference in .skills/security-audit.json:

{
  "custom_attack_classes": [
    {
      "name": "API Gateway Abuse",
      "file": ".skills/custom-attacks/api-gateway-abuse.md"
    }
  ]
}

Troubleshooting

Issue: Too many false positives

Symptom: Findings include theoretical vulnerabilities without exploitation paths.

Solution: The validation phase should catch these. If not:

1. Check validation logs in validation-logs/ for validator agent reasoning
2. Strengthen validation prompt: "Prove this finding is NOT exploitable"
3. Set SECURITY_AUDIT_MIN_SEVERITY=MEDIUM to filter noise

Issue: Missing obvious vulnerabilities

Symptom: Known vulnerabilities not in findings.

Solution:

1. Check coverage_notes in findings.json — may be deferred to another run
2. Review architecture.md — recon may have missed the affected component
3. Run additional audits with explicit focus: audit ./src/vulnerable-module
4. Check if prior runs marked it as rejected (see rejected_findings)

Issue: Validation phase rejects everything

Symptom: All findings end up in rejected_findings.

Solution:

1. Review rejection_reason — often "no concrete exploitation path"
2. Hunters must provide actual payloads, not descriptions
3. Check if defense-in-depth layers are blocking attacks (this is correct rejection)
4. Ensure findings include proof_of_concept with real inputs

Issue: Schema validation fails

Symptom: validate-findings.cjs reports errors.

Solution:

# Run validator with verbose output
node validate-findings.cjs findings.json --verbose

# Common errors:
# - Missing required fields (id, title, severity, location, exploit_scenario)
# - Invalid severity (must be CRITICAL, HIGH, MEDIUM, LOW, INFO)
# - Malformed location (missing file or line_start)
# - Empty evidence.vulnerable_code

Fix by ensuring structured output phase strictly follows report-schema.json.

Issue: Agents go off-task

Symptom: Agents suggest refactoring, performance improvements, or non-security issues.

Solution: The skill enforces focus via system prompts. If this happens:

1. Check agent logs for prompt drift
2. Re-run with explicit constraint: security audit focused only on exploitable vulnerabilities
3. Review ATTACK-CLASSES.md definitions — agents should stay within attack class scope

Issue: Duplicate findings across runs

Symptom: Same vulnerability reported in multiple runs.

Solution:

1. Ensure prior_runs_reviewed in findings.json lists previous runs
2. Check SECURITY_AUDIT_PRIOR_RUNS_DIR points to correct location
3. Verify finding IDs are stable (based on file + location, not random)
4. Manual deduplication via id field in findings.json

Issue: Can't reproduce PoC

Symptom: proof_of_concept in findings doesn't work when tested.

Solution:

1. This is a validation failure — escalate to independent verification phase
2. Check verification_status field — should be independently_verified
3. If verification passed but PoC fails, file issue with verification logs
4. Ensure PoC includes all preconditions (auth tokens, session state, etc.)

Advanced usage

Diff-based auditing

Audit only changed code between commits:

# Get changed files
git diff --name-only HEAD~5 HEAD > changed-files.txt

# Configure skill to focus on those files
export SECURITY_AUDIT_FOCUS_FILES=$(cat changed-files.txt | tr '\n' ',')

# Run audit
security audit changed code since 5 commits ago

Integration with existing security tools

Combine with SAST/DAST tools:

// scripts/merge-findings.js
const skillFindings = require('./audit-results/findings.json');
const sastResults = require('./sast-output.json');

const merged = {
  ...skillFindings,
  confirmed_findings: [
    ...skillFindings.confirmed_findings,
    ...sastResults.issues
      .filter(issue => issue.confidence === 'HIGH')
      .map(issue => ({
        id: `SAST-${issue.id}`,
        title: issue.title,
        severity: mapSeverity(issue.severity),
        category: issue.category,
        location: {
          file: issue.file,
          line_start: issue.line,
          line_end: issue.line
        },
        // ... map other fields
        verification_status: 'tool_reported'
      }))
  ]
};

console.log(JSON.stringify(merged, null, 2));

Custom reporting

Generate reports in different formats:

// scripts/generate-html-report.js
const findings = require('./findings.json');
const fs = require('fs');

const html = `
<!DOCTYPE html>
<html>
<head><title>Security Audit Report</title></head>
<body>
  <h1>Security Audit: ${findings.audit_metadata.target_repository}</h1>
  <p>Date: ${findings.audit_metadata.audit_date}</p>
  
  <h2>Critical Findings (${findings.confirmed_findings.filter(f => f.severity === 'CRITICAL').length})</h2>
  ${findings.confirmed_findings
    .filter(f => f.severity === 'CRITICAL')
    .map(f => `
      <div class="finding">
        <h3>${f.id}: ${f.title}</h3>
        <p><strong>Location:</strong> ${f.location.file}:${f.location.line_start}</p>
        <p><strong>Impact:</strong> ${f.exploit_scenario.impact}</p>
        <pre>${f.evidence.vulnerable_code}</pre>
      </div>
    `).join('\n')}
</body>
</html>
`;

fs.writeFileSync('audit-report.html', html);

Requirements

• Coding agent with tool use and parallel sub-agent support (Claude Code, Cursor, Codex, etc.)
• Node.js (for schema validation)
• Git (for multi-run deduplication)

Related skills

• sast-integration-skill — Integrates SAST tool output with adversarial validation
• threat-modeling-skill — Architecture-level threat modeling before code audit
• exploit-development-skill — Turns findings into working exploits for penetration testing

License

MIT — see LICENSE