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Introduction:
Broken Access Control (BAC) remains the most critical web application security risk, as recognized by OWASP. A recent case study involving a 17-year-old researcher who uncovered multiple P1-level vulnerabilities in NASA’s systems demonstrates how mastering BAC techniques can lead to significant security discoveries. This article provides technical guidance for identifying and exploiting these critical flaws.
Learning Objectives:
- Understand the fundamental mechanisms behind Broken Access Control vulnerabilities
- Master practical command-line and tool-based techniques for BAC testing
- Develop methodology for comprehensive access control testing across applications
You Should Know:
1. Understanding User Role Enumeration
Browser Console JavaScript to check user privileges
const userRoles = JSON.parse(localStorage.getItem('userProfile')).roles;
console.log('Available roles:', userRoles);
const availableEndpoints = await fetch('/api/endpoints/available');
console.log('Accessible endpoints:', await availableEndpoints.json());
Step-by-step guide: This JavaScript code helps identify stored user roles and accessible endpoints directly from the browser’s local storage. Execute this in the browser console while logged into an application to enumerate your current privileges and discover potentially accessible API endpoints that might be vulnerable to privilege escalation.
2. API Parameter Testing with curl
Testing IDOR vulnerabilities with sequential ID testing
for id in {1000..1010}; do
curl -H "Authorization: Bearer $TOKEN" -s \
"https://target.com/api/user/$id/profile" | jq .
sleep 1
done
Step-by-step guide: This bash loop tests sequential user IDs for potential Insecure Direct Object Reference (IDOR) vulnerabilities. Replace $TOKEN with your authentication token and observe responses for different IDs. Successful responses with different user data indicate missing access controls.
3. Hidden Path Discovery with ffuf
ffuf -w /usr/share/wordlists/common-api-paths.txt \ -u https://target.com/api/FUZZ \ -H "Authorization: Bearer $TOKEN" \ -mc all -fc 403,404 -t 50
Step-by-step guide: This ffuf command tests for hidden API endpoints that might not be properly protected. The wordlist contains common API paths, and the filter removes common error codes. Any discovered endpoints should be tested for authorization bypass.
4. Token Manipulation Testing
JWT Token decoding and manipulation
echo "eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJzdWIiOiIxMjM0NTY3ODkwIiwicm9sZSI6InVzZXIiLCJpYXQiOjE1MTYyMzkwMjJ9" | base64 -d
Modify role to "admin" and re-encode
echo '{"sub":"1234567890","role":"admin","iat":1516239022}' | base64
Step-by-step guide: This demonstrates basic JWT token decoding and manipulation. Always test if applications properly validate token signatures or if role parameters can be modified to elevate privileges.
5. Mass Assignment Testing
Testing for mass assignment vulnerabilities
curl -X POST https://target.com/api/user/profile \
-H "Content-Type: application/json" \
-H "Authorization: Bearer $TOKEN" \
-d '{"username":"test","email":"[email protected]","role":"admin","is_admin":true}'
Step-by-step guide: This curl command tests if applications properly filter incoming request parameters. Add privileged parameters like “role”, “is_admin”, or “permissions” to see if the application accepts them without proper validation.
6. GraphQL Authorization Testing
Testing GraphQL endpoints for BAC
curl -X POST https://target.com/graphql \
-H "Content-Type: application/json" \
-H "Authorization: Bearer $TOKEN" \
-d '{"query":"query { users { email password admin } }"}'
Step-by-step guide: GraphQL endpoints often expose data without proper authorization checks. Test by querying sensitive fields that should be restricted to privileged users.
7. Automated BAC Testing with Nuclei
nuclei -u https://target.com -t /path/to/bac-templates \ -header "Authorization: Bearer $TOKEN" -rate-limit 10
Step-by-step guide: Use Nuclei with custom BAC templates to automate testing for common access control vulnerabilities. Always test with proper authorization headers and respect rate limits.
What Undercode Say:
- Broken Access Control consistently ranks as the most critical web vulnerability because it directly compromises data confidentiality and integrity
- Successful BAC identification requires deep understanding of application business logic rather than just technical scanning
- The human element of persistence and consistency often outweighs technical skill alone in vulnerability discovery
The demonstrated techniques show that BAC vulnerabilities persist in even the most high-profile targets. The researcher’s success with NASA systems highlights that comprehensive access control testing requires both automated tools and manual business logic analysis. Organizations must implement proper role-based access control, parameter validation, and regular security testing to prevent such critical vulnerabilities.
Prediction:
Broken Access Control vulnerabilities will increasingly target API endpoints and microservices architectures as applications continue to move away from traditional monolithic designs. The rise of GraphQL and other query languages will create new attack surfaces for authorization bypass, while AI-assisted code generation may inadvertently introduce more access control flaws through improperly venerated code patterns.
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IT/Security Reporter URL:
Reported By: Azza Tegar – Hackers Feeds
Extra Hub: Undercode MoN
Basic Verification: Pass ✅
