CWE-580: clone() Method Without super.clone()

What is clone() Method Without super.clone()?

• Overview: The CWE-580 vulnerability occurs when a clone() method in Java does not call super.clone() to create a new object. This can lead to incorrect object types being returned when subclass objects are cloned, potentially violating object integrity and leading to unpredictable behavior.

• Exploitation Methods:

• Attackers may exploit this vulnerability by inducing unexpected behavior in applications that rely on object cloning, potentially leading to crashes or incorrect processing.
• Common attack patterns include crafting inputs that exploit the incorrect type returned by clone(), causing logic errors or security bypasses.

• Security Impact:

• Direct consequences include the creation of objects of the wrong type, which may lead to incorrect application logic or runtime exceptions.
• Potential cascading effects include data corruption or loss of data integrity if cloned objects are used in critical application paths.
• Business impact may include loss of customer trust, financial loss due to downtime or data breaches, and increased maintenance costs.

• Prevention Guidelines:

• Ensure that all clone() implementations in Java call super.clone() to obtain the new object of the correct type.
• Follow security best practices by reviewing all custom clone() methods for compliance with the standard cloning pattern.
• Use tools such as static code analyzers to detect instances of clone() methods not calling super.clone(), and incorporate these checks into the development pipeline.

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Technical Details

Likelihood of Exploit: Not specified

Affected Languages: Java

Affected Technologies: Not specified

Vulnerable Code Example

// CloneableUser.java {8-13}
public class CloneableUser implements Cloneable {
    private String name;
    private int age;

    // Vulnerable clone method
    @Override
    protected Object clone() throws CloneNotSupportedException {
        // This method does not call super.clone(), which may lead to incomplete cloning
        // and issues with the internal state of the cloned object not being correctly initialized.
        CloneableUser clonedUser = new CloneableUser();
        clonedUser.name = this.name;
        clonedUser.age = this.age;
        return clonedUser;
    }

    // Getters and setters omitted for brevity
}

How to fix clone() Method Without super.clone()?

To fix the vulnerability in the clone() method, it is essential to invoke super.clone() to ensure that the new object is a true copy of the original object. The super.clone() method creates a shallow copy of the object, handling the internal state correctly, and ensures that the object is an instance of the right class.

By calling super.clone(), we leverage the Cloneable interface properly, which is designed to provide field-by-field copying by default, avoiding issues related to object state initialization.

Best Practices for Cloning in Java:

1. Always call super.clone() to let the base class do the initial cloning.
2. Handle CloneNotSupportedException appropriately, often by catching it and converting it to a runtime exception.
3. Consider using copy constructors or factory methods as alternatives to clone() for better control over object creation.

Fixed Code Example

// CloneableUser.java {8-15}
public class CloneableUser implements Cloneable {
    private String name;
    private int age;

    // Fixed clone method
    @Override
    protected Object clone() throws CloneNotSupportedException {
        // Call to super.clone() ensures that all fields are copied correctly
        CloneableUser clonedUser = (CloneableUser) super.clone();
        // Additional handling for mutable fields or deep copies can be added here if necessary
        return clonedUser;
    }

    // Getters and setters omitted for brevity
}

In the fixed version, we call super.clone() to ensure proper cloning. If the class contains any mutable objects or requires deep copying, additional logic should be added after super.clone(). This approach ensures that the clone operation is safe and behaves as expected.