What is Explicit Call to Finalize() (CWE-586)?

TL;DR: Explicit Call to Finalize() (CWE-586) is a type of vulnerability that occurs when Java code explicitly invokes the finalize() method outside its intended lifecycle. It can cause unexpected behavior and quality degradation, impacting software integrity and reliability.

What is Explicit Call to Finalize()?

Explicit Call to Finalize() (CWE-586) is a type of vulnerability that occurs when the finalize() method in Java is called explicitly from outside its intended lifecycle. As defined by the MITRE Corporation under CWE-586, and classified by the OWASP Foundation as not directly mapped.

Quick Summary

Explicit Call to Finalize() happens when developers invoke the finalize() method directly rather than relying on the JVM’s garbage collector for proper resource management. This can lead to unexpected behavior and quality degradation due to improper object finalization. Jump to: Overview · How It Works · Business Impact · Attack Scenario · Detection · Fixes

Jump to: Quick Summary · Explicit Call to Finalize() Overview · How Explicit Call to Finalize() Works · Business Impact of Explicit Call to Finalize() · Explicit Call to Finalize() Attack Scenario · How to Detect Explicit Call to Finalize() · How to Fix Explicit Call to Finalize() · Framework-Specific Fixes for Explicit Call to Finalize() · How to Ask AI to Check Your Code for Explicit Call to Finalize() · Explicit Call to Finalize() Best Practices Checklist · Explicit Call to Finalize() FAQ · Vulnerabilities Related to Explicit Call to Finalize() · References · Scan Your Own Site

Explicit Call to Finalize() Overview

• What: An explicit call to finalize() occurs when the finalize() method is invoked directly from outside its intended lifecycle.
• Why it matters: Improper resource management and object finalization can lead to unexpected behavior, quality degradation, and potential security vulnerabilities.
• Where it occurs: Java applications that make direct calls to finalize().
• Who is affected: Developers and organizations using Java who inadvertently invoke finalize() explicitly.
• Who is NOT affected: Applications that do not make explicit calls to finalize().

How Explicit Call to Finalize() Works

Root Cause

The root cause of this vulnerability lies in the improper invocation of the finalize() method outside its intended lifecycle. This disrupts proper resource management and object finalization.

Attack Flow

1. Developer invokes finalize() directly.
2. JVM does not manage resources as expected.
3. Unexpected behavior or quality degradation occurs due to improper finalization.

Prerequisites to Exploit

• The application must make a direct call to finalize().
• The code invoking finalize() should be outside the intended lifecycle of object disposal.

Vulnerable Code

public class Example {
    protected void finalize() throws Throwable {
        System.out.println("Finalizing...");
    }

    public static void main(String[] args) {
        Example obj = new Example();
        obj.finalize();  // Explicit call to finalize()
    }
}

This code demonstrates a direct invocation of the finalize() method, which is outside its intended lifecycle.

Secure Code

public class Example {
    protected void finalize() throws Throwable {
        System.out.println("Finalizing...");
    }

    public static void main(String[] args) {
        Example obj = new Example();
        // No explicit call to finalize()
    }
}

In the secure version, there is no direct invocation of finalize(), relying on the JVM’s garbage collector for proper resource management.

Business Impact of Explicit Call to Finalize()

• Integrity: Improper finalization can lead to unexpected states and quality degradation.
• Other: Potential security vulnerabilities due to improper resource management.

Real-world business consequences include financial losses, compliance issues, and reputational damage from software failures caused by this vulnerability.

Explicit Call to Finalize() Attack Scenario

1. Developer writes Java code that explicitly calls finalize().
2. The JVM does not manage resources as expected.
3. Unexpected behavior or quality degradation occurs due to improper finalization.

How to Detect Explicit Call to Finalize()

Manual Testing

• Review the source code for direct invocations of finalize().
• Ensure no explicit calls are made outside the intended lifecycle of object disposal.

Automated Scanners (SAST / DAST)

Static analysis can detect explicit calls to finalize(), while dynamic testing may be necessary to confirm the impact in a running application environment.

PenScan Detection

PenScan’s scanner engines such as ZAP, Nuclei, and Wapiti can identify explicit calls to finalize() during automated scans.

False Positive Guidance

A false positive occurs if the code is correctly using finalize() within its intended lifecycle or if it is a legitimate use case that does not introduce vulnerabilities.

How to Fix Explicit Call to Finalize()

• Do not make explicit calls to finalize().
• Rely on the JVM’s garbage collector for proper resource management.

Framework-Specific Fixes for Explicit Call to Finalize()

public class Example {
    protected void finalize() throws Throwable {
        System.out.println("Finalizing...");
    }

    public static void main(String[] args) {
        Example obj = new Example();
        // No explicit call to finalize()
    }
}

In Java, ensure that finalize() is not invoked explicitly and rely on the JVM’s garbage collector for proper resource management.

How to Ask AI to Check Your Code for Explicit Call to Finalize()

Explicit Call to Finalize() Best Practices Checklist

• ✅ Do not make explicit calls to finalize().
• ✅ Rely on the JVM’s garbage collector for proper resource management.

Explicit Call to Finalize() FAQ

How does an explicit call to finalize() occur?

An explicit call to finalize() occurs when a developer invokes the finalize() method directly from outside of its intended lifecycle.

Why is it dangerous to explicitly call finalize() in Java code?

It can lead to unexpected behavior and quality degradation due to improper resource management and object finalization.

How do I detect explicit calls to finalize() in my codebase?

Use static analysis tools or manual review to identify direct invocations of the finalize() method outside its intended lifecycle.

What are the consequences of an explicit call to finalize()?

It can cause unexpected states and quality degradation, impacting software integrity and reliability.

How do I prevent CWE-586 in my Java codebase?

Do not make explicit calls to finalize(). Rely on the JVM’s garbage collector for proper resource management.

Can you provide an example of vulnerable code that invokes finalize() explicitly?

Vulnerable code would directly call finalize() from outside its intended lifecycle, such as in a cleanup method or destructor.

How can I validate if my Java application is free from explicit calls to finalize()?

Review your codebase for any direct invocations of the finalize() method and ensure it’s only used within the JVM’s garbage collection process.

Vulnerabilities Related to Explicit Call to Finalize()

References

• MITRE - CWE-586
• CAPEC - None known
• NVD

Scan Your Own Site

Manual code review catches what you know to look for. An automated scan catches what you didn’t. Scan your own website using PenScan to find Explicit Call to Finalize() and other risks before an attacker does.