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What is Command Injection?

Command Injection lets attackers run system commands via apps. Learn what it is, how it works, and how to prevent it effectively.

Explain Like I'm 5

Imagine your computer is like a restaurant, and each task it performs is a chef preparing a dish. You normally place your order by telling the waiter what you want. But if you could sneak into the kitchen and tell the chef directly to add or change ingredients, you could create a dish that wasn't on the menu. Command Injection is like sneaking into the kitchen. It's when someone finds a way to talk to the computer's 'chefs' directly, making it do things it wasn't supposed to, like serving a surprise dish that could cause trouble.

Why does this matter? Just like a surprise dish with bad ingredients could ruin a meal, a command injected into a system can cause it to malfunction or expose sensitive information. It means someone could secretly make your computer do things that compromise its security, like leaking your private files or even crashing the entire system.

Technical Definition

Definition

Command Injection is a security vulnerability where an attacker can execute arbitrary commands on a host's operating system through a vulnerable application. This happens when user input is improperly sanitized and passed to a system shell.

How It Works

  1. 1User input is received by the application.
  2. 2The input is concatenated into a command string that will be executed by the system shell.
  3. 3If the input is not properly sanitized, the attacker can append malicious commands.
  4. 4The system shell executes both the intended command and the injected command.

Key Characteristics

  • Exploits system shell command execution.
  • Occurs due to improper input validation.
  • Can be blind (no direct output) or visible (output visible to attacker).
  • Often involves chaining operators like &&, ||, |, and ;.

Comparison

FeatureCommand InjectionSQL Injection
TargetOS CommandsDatabase Queries
Common LanguageShell CommandsSQL
Potential ImpactSystem ControlData Access/Modification
Example VulnerabilityCVE-2014-6271CVE-2014-0160

Real-World Example

CVE-2014-6271, known as Shellshock, is a notorious example of command injection. It allowed attackers to execute arbitrary commands on servers using vulnerable versions of Bash, a popular Unix shell.

Detection & Prevention

  • Detection: Use tools like Burp Suite, OWASP ZAP, or nuclei to scan for vulnerabilities. Implement logging to detect unusual command execution.
  • Prevention: Validate and sanitize all user inputs. Use parameterized queries and avoid using system shell commands when possible.

Common Misconceptions

  • Command Injection is not the same as SQL Injection; they target different layers.
  • Not all command injections provide immediate visible results; blind injections require indirect observation of effects.
  • Using HTTPS does not protect against command injection; it only secures data in transit.

Keywords

what is Command InjectionCommand Injection explainedCommand Injection detectionCommand Injection preventionOS command injectionblind command injectionShellshock CVE-2014-6271

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