CWE-1235: Incorrect Use of Autoboxing and Unboxing for Performance Critical Operations

What is Incorrect Use of Autoboxing and Unboxing for Performance Critical Operations?

• Overview: Incorrect Use of Autoboxing and Unboxing for Performance Critical Operations (CWE-1235) refers to the use of automatic conversion between primitive types and their corresponding wrapper classes in programming languages like Java and C#. This can lead to performance inefficiencies, especially in performance-critical operations, due to the extra overhead of object creation and garbage collection.

• Exploitation Methods:

• Attackers cannot directly exploit autoboxing/unboxing like a traditional security vulnerability, but inefficient use can lead to degraded performance, which might be exploited in denial of service scenarios.
• Common attack patterns include causing a system to slow down or become unresponsive by exploiting code paths that involve excessive autoboxing/unboxing in a performance-critical application.

• Security Impact:

• Direct consequences of excessive autoboxing/unboxing include increased memory usage and CPU load, leading to slower application performance.
• Potential cascading effects might include resource exhaustion, which could impact application availability and responsiveness.
• Business impact may involve reduced user satisfaction due to slow application performance, increased operational costs from inefficient resource use, and potential revenue loss if the application is part of a critical business function.

• Prevention Guidelines:

• Specific code-level fixes involve minimizing the use of boxed primitives in performance-critical code paths. Use primitive types directly instead of their wrapper classes whenever possible.
• Security best practices include profiling and optimizing critical code sections to identify and eliminate unnecessary autoboxing/unboxing operations.
• Recommended tools and frameworks involve using performance profiling tools to analyze and optimize code performance. Additionally, consider using collections and libraries designed to work efficiently with primitive types.

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Technical Details

Likelihood of Exploit: Not specified

Affected Languages: Java, C#

Affected Technologies: Not Technology-Specific

Vulnerable Code Example

Java Example

import java.util.ArrayList;
import java.util.List;

public class PerformanceCriticalOperations {
    public static void main(String[] args) {
        List<Integer> numbers = new ArrayList<>();
        // Adding numbers to the list
        for (int i = 0; i < 100000; i++) {
            numbers.add(i); // Autoboxing occurs here
        }

        long sum = 0;
        for (int number : numbers) { // Unboxing occurs here
            sum += number; // Unboxing occurs here
        }

        System.out.println("Sum: " + sum);
    }
}

Explanation:

• Autoboxing: Occurs when a primitive type is automatically converted to its corresponding wrapper class (e.g., int to Integer). This happens when adding int values to a List<Integer>.
• Unboxing: Occurs when an object of a wrapper class is converted back to a primitive type. This happens during the iteration and summation of List<Integer> elements.
• In performance-critical operations, such as iterating over large collections, autoboxing and unboxing can degrade performance due to the overhead of creating wrapper objects and increased garbage collection.

How to fix Incorrect Use of Autoboxing and Unboxing for Performance Critical Operations?

To address the performance issues caused by autoboxing and unboxing, use primitive arrays or collections designed specifically for primitive types. This avoids the overhead associated with converting between primitives and their wrapper classes.

Fixed Code Example

public class PerformanceCriticalOperations {
    public static void main(String[] args) {
        // Use a primitive array to store integers directly
        int[] numbers = new int[100000];

        // Populating the array with values
        for (int i = 0; i < numbers.length; i++) {
            numbers[i] = i; // No autoboxing
        }

        long sum = 0;
        for (int number : numbers) {
            sum += number; // No unboxing
        }

        System.out.println("Sum: " + sum);
    }
}

Key Changes:

• Replaced List<Integer> with int[] to directly store and manipulate primitive integers.
• Eliminated autoboxing and unboxing by using primitive types, which enhances performance by reducing object creation and garbage collection overhead.
• This approach is more efficient for performance-critical applications, especially when dealing with large datasets.