CWE-78 Improper Neutralization of OS Command

Description

Improper Neutralization of OS Command

Reference: https://cwe.mitre.org/data/definitions/78.html

OWASP Category: A03:2021 – Injection

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Vulnerable Pattern

❌ Example 1: Vulnerable Pattern

// VULNERABLE: Shell metacharacters not neutralized
String filename = request.getParameter("file");
Runtime.getRuntime().exec("cat " + filename);

Why it's vulnerable: This pattern is vulnerable to Improper Neutralization of OS Command

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Deterministic Fix

✅ Secure Implementation: Secure Implementation

// SECURE: Validate and use ProcessBuilder
String filename = request.getParameter("file");
if (!filename.matches("^[a-zA-Z0-9_.-]+$")) {
    throw new SecurityException("Invalid filename");
}
ProcessBuilder pb = new ProcessBuilder("cat", filename);
Process p = pb.start();

Why it's secure: Implements proper protection against Improper Neutralization of OS Command

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Detection Pattern

Look for these patterns in your codebase:

# Find exec with user input
grep -rn "exec.*getParameter\\|exec.*request" --include="*.java"

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Remediation Steps

1. Validate input against whitelist of allowed characters

2. Use parameterized command execution (ProcessBuilder)

3. Escape shell metacharacters if shell execution is unavoidable

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Key Imports

import java.lang.ProcessBuilder;

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Verification

After remediation:

• Run SAST scanner to confirm vulnerability is resolved

• Review all instances of the vulnerable pattern

• Add unit tests that verify the secure implementation

• Check for similar patterns in related code

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Trigger Examples

Fix CWE-78 vulnerability
Resolve Improper Neutralization of OS Command issue
Secure this Java code against improper neutralization of os command
SAST reports CWE-78

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Common Vulnerable Locations

Layer	Files	Patterns

| Controller | *Controller.java | User input handling |

| Service | *Service.java | Business logic |

| Repository | *Repository.java | Data access |

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References

• CWE-78: OS Command Injection

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Source: Generated by Java CWE Security Skills Generator Last Updated: 2026-03-07