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Broken Access Control: The Silent Killer of Web Applications By CyberDudeBivash – Your Daily Dose of Ruthless, Engineering-Grade Threat Intel

 


1. Introduction

Broken Access Control (BAC) is consistently ranked #1 in the OWASP Top 10 because when access control fails, attackers can directly access sensitive data, perform unauthorized actions, or compromise entire systems.

Access control determines who can do what in an application. When it’s broken, attackers exploit logic flaws, insecure policy enforcement, or bypass controls entirely. In 2025, with APIs, microservices, and cloud-hosted platforms dominating the web stack, BAC risks are amplified — especially in multi-tenant SaaS and API-driven architectures.

2. How Broken Access Control Works

Access Control Types

  • Vertical Access Control – Restricts access based on role/privilege (e.g., admin vs user).

  • Horizontal Access Control – Restricts access to data/resources owned by the same privilege level (e.g., user should only see their own profile).

  • Context-Based Access Control – Restricts actions based on conditions (time, IP, device).

When “Broken” means:

  • Missing role checks.

  • Flawed object ID enforcement (Insecure Direct Object References – IDOR).

  • Misconfigured security rules.

  • Client-side-only enforcement.

3. Common Broken Access Control Attack Vectors

3.1 Insecure Direct Object References (IDOR)

An attacker modifies a parameter (e.g., ?user_id=1002) to access another user’s records.

Example:

GET /account?user_id=1002  → Returns another user's data.

3.2 Privilege Escalation

A normal user manipulates requests to gain admin-level access.

Example:
Changing

"role":"user"

to

"role":"admin"

in a JSON request body.

3.3 Bypassing Access Controls with Alternate Methods

  • Directly accessing API endpoints not exposed in the UI.

  • Exploiting cached or debug URLs.

3.4 Force Browsing

Manually navigating to restricted URLs (e.g., /admin) without authentication checks.

3.5 API Over-Exposure

APIs returning more fields than necessary — attackers filter data on the client side to find sensitive info.

4. Real-World Case Studies

  • Facebook 2018 – BAC flaw let attackers steal access tokens of millions of accounts.

  • Indian Government Portals – Multiple IDOR-based data leaks of Aadhaar numbers.

  • GitHub 2021 – Privilege escalation in GitHub Actions affecting private repositories.

5. Advanced Exploitation Techniques in 2025

TechniqueDescriptionImpact
JWT ManipulationModifying unsigned/weakly signed tokens to escalate privileges.Full account takeover.
CORS MisconfigurationsAccessing privileged APIs from malicious origins.Data theft via cross-domain calls.
Chained ExploitsCombining BAC with SSRF or RCE for deeper compromise.Complete environment breach.
GraphQL OverfetchingQuerying sensitive fields bypassing role checks.API data leakage.

6. MITRE ATT&CK Mapping

  • T1078 – Valid Accounts (abuse of compromised credentials)

  • T1190 – Exploit Public-Facing Application

  • T1552 – Unsecured Credentials in Data Stores

  • T1069 – Permission Groups Discovery

7. Detection & Prevention Strategies

A. Server-Side Enforcement

  • Validate all authorization decisions server-side — never rely on the client.

B. Principle of Least Privilege

  • Assign only the minimum permissions needed for a role.

  • Regularly review and revoke unused privileges.

C. IDOR Prevention

  • Use indirect references (UUID tokens) instead of incremental IDs.

  • Validate ownership of every object request.

D. API Access Control

  • Apply role-based access checks at every API endpoint.

  • Use attribute-based access control (ABAC) for dynamic conditions.

E. Logging & Monitoring

  • Log access control violations for detection and investigation.

  • Integrate with SIEM to detect patterns of enumeration.

8. Threat Hunting Tips

  • Look for repeated 403/401 responses from the same IP — could indicate brute-force privilege testing.

  • Monitor for URL tampering attempts in HTTP logs.

  • Flag unexpected access to sensitive APIs by low-privilege accounts.

9. CyberDudeBivash Recommendations

  • Red Team: Test APIs and UI endpoints for IDOR, privilege escalation, and hidden resources.

  • Blue Team: Monitor privilege change events and abnormal API usage.

  • DevSecOps: Integrate automated access control testing into CI/CD pipelines.

Conclusion

Broken Access Control is like leaving the front door open while having the best locks in the world — it nullifies all other defenses. Whether you run a banking app, e-commerce platform, or SaaS product, enforce strict access policies, validate everything server-side, and continuously test for weaknesses.

Remember: In the access control game, attackers only need one bypass. Defenders need to seal every path.

🔗 Powered by CyberDudeBivash – Global Threat Intel, Incident Analysis, and Cybersecurity Engineering.
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