Course 39 - NodeJS Security Pentesting and Exploitation | Episode 2: Mitigating RCE, OS Injection, and Path Traversal Vulnerabilities — CyberCode Academy

In this lesson, you’ll learn about: critical Node.js vulnerabilities caused by unsafe user input handling, including RCE, command injection, XSS, and directory traversal1. Core Security Principle🔹 Key idea:
Never trust user input👉 Any data from users must be treated as hostile by default
Without validation, it can become a direct execution path into the system.2. Remote Code Execution (RCE) via eval()🔹 Dangerous functions:

eval()
setTimeout()
setInterval()
new Function()

🔹 Why they are riskyThese functions execute raw JavaScript strings🔹 Attack outcomes:

Infinite loops → server crash (DoS)
Forced termination (process.exit())
Full server takeover (reverse shell execution)

👉 Key Insight
If user input reaches an execution function → the server is effectively “remote-controlled”3. Remote OS Command Injection🔹 Vulnerable function:

child_process.exec

🔹 How the attack works:

Input is passed into shell commands
Attacker injects separators like ;
Extra commands execute on the OS

🔹 Example impact:

Read sensitive files (e.g., system password data)
Execute arbitrary system commands

🔹 Safer alternatives:

execFile
spawn

👉 Why they are safer:
They treat input as arguments, not executable shell strings4. Cross-Site Scripting (XSS)🔹 Cause:
Unsanitized user input reflected into browser output🔹 Impact:

Script execution in victim’s browser
Session hijacking potential
UI manipulation

👉 Key Insight
Server-side mistake becomes client-side compromise5. Directory Traversal (Path Traversal)🔹 Technique:
Using patterns like:

../
repeated directory jumps

🔹 Impact:

Access files outside intended directory
Read sensitive system files
Break application file boundaries

6. Big PictureThis episode shows how Node.js apps fail when:

Input is executed instead of validated
System commands are built from raw strings
Output is rendered without escaping
File paths are not restricted

Mental ModelUser input → execution boundary → system access
If that chain is not broken at validation → full compromise becomes possible

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