CVE 2021-42013 | Subdomain takeover vulnerabilities | SQL Injection in Insert, Update and Delete Statements ...

 🔐 “CVE-2021-42013, Subdomain Takeover, and Advanced SQL Injection in Insert/Update/Delete: A Deep Dive”

🧠 Goal of This Content:

To educate and alert security professionals about:

1. A known critical vulnerability (CVE-2021-42013)

2. Subdomain takeover attacks — how they happen and how to prevent them

3. Advanced SQL injection techniques in non-select queries (INSERT, UPDATE, DELETE), which are often overlooked

This could be packaged as a technical threat report, blog post, conference talk, or training module.

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✅ Recommended Structure for High-Impact Blog/Report

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🧨 1. Introduction: A Triple Threat to Web Security

“Modern applications face more than login brute force and weak passwords. Exploits like CVE-2021-42013, forgotten subdomains, and blind SQL injections in non-SELECT queries are now common tools in an attacker’s arsenal.”

• Highlight the increasing complexity of chained vulnerabilities

• Preview how these three vectors are often connected in the real world (especially in bug bounty & red team ops)

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🔍 2. CVE-2021-42013 – Apache Path Traversal → Remote Code Execution

• Vulnerability: Apache HTTP Server 2.4.49/2.4.50

• Impact: Path traversal & RCE via crafted URI

• Payload Example:

  bash
  
  GET /.%2e/.%2e/.%2e/.%2e/etc/passwd HTTP/1.1
  

• Root Cause: Incomplete patch from CVE-2021-41773

• Fix: Upgrading to 2.4.51 or later

✅ Exploit Use Case:

• Used in initial access during web app testing

• Often combined with file upload or server misconfiguration

📌 Link: https://nvd.nist.gov/vuln/detail/CVE-2021-42013

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🌐 3. Subdomain Takeover Vulnerabilities – The Silent Exploit

• Definition: A subdomain (blog.example.com) points to a third-party service (like GitHub Pages, Heroku, or AWS), but the service is no longer active.

• What happens: An attacker registers the service (like a GitHub repo with the same name) and gets control over that subdomain.

✅ How It Happens:

• DNS record (CNAME) still points to the external service

• No resource exists on the service (e.g., deleted GitHub repo)

• Attacker sets it up → takes over the subdomain

🛠 Tools to Detect:

• Subjack, SubOver, Amass, Aquatone

🔥 Real-World Consequences:

• Used to host phishing pages

• Cookie stealing via same-origin XSS

• TLS abuse with Let's Encrypt

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💉 4. Advanced SQL Injection in INSERT / UPDATE / DELETE

Most people scan for SELECT-based injections — but INSERT/UPDATE/DELETE SQLi are:

• Blind

• Harder to detect

• More dangerous if tied to business logic

🧬 Examples:

🔸 INSERT SQLi:

sql

INSERT INTO users (name, email) VALUES ('$name', '$email');

Injection payload:

sql

test@example.com'); DROP TABLE users; --

🔸 UPDATE SQLi:

sql

UPDATE users SET password='$password' WHERE id='$id';

Injection:

sql

1 OR 1=1; --

🔸 DELETE SQLi:

sql

DELETE FROM orders WHERE order_id='$order_id';

Injection:

sql

0 OR 1=1

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🧪 5. Detection & Defense Tips

Attack Type	Detection Method	Defense Technique
CVE-2021-42013	Log inspection, directory traversal fuzz	Patch to 2.4.51+, WAF filtering
Subdomain Takeover	Subjack scans, DNS audits	Periodic DNS cleanup, third-party audits
SQLi in Updates	Behavior analysis, blind time-based tests	Parameterized queries, ORM frameworks

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⚠️ 6. Red Team / Bug Bounty POV: Chained Exploits

✅ Exploit Path Scenario:

1. Find outdated Apache server → exploit CVE-2021-42013 for access

2. Find old staging subdomain → takeover → host malicious JS

3. Blind SQL injection in admin panel’s update function → exfil data

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🔐 7. Final Thoughts: Know the Depth, Not Just the Surface

“Security doesn’t just mean blocking login attempts. It means checking every forgotten subdomain, every patch, and every form field.”

• Recommend regular recon (Subfinder, FFUF)

• Recommend ML-assisted anomaly detection for SQLi

• Promote zero trust on internal IP ranges/subdomains

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📈 SEO Tags & Meta

Keywords:

• CVE-2021-42013 explained

• subdomain takeover automation

• insert update delete SQL injection

• blind SQLi real world

• apache path traversal CVE

• chained vulnerabilities pentest

Tags:

#CVE2021 #SubdomainTakeover #SQLInjection #CyberSecurity #RedTeamOps #BugBounty #AppSec

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1. CVE 

2. Subdomain 

3. SQL Injection

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