CWE-583: finalize() Method Declared Public
Learn about CWE-583 (finalize() Method Declared Public), its security impact, exploitation methods, and prevention guidelines.
What is finalize() Method Declared Public?
• Overview: The vulnerability CWE-583 occurs when the finalize() method in Java is declared public, which goes against secure coding practices by allowing potentially malicious access to finalize operations.
• Exploitation Methods:
- Attackers can exploit this vulnerability by invoking the finalize() method directly, leading to unauthorized or unexpected resource release or cleanup actions.
- Common attack patterns include triggering garbage collection routines at inappropriate times or in unintended ways, potentially disrupting normal program behavior.
• Security Impact:
- Direct consequences include unauthorized resource deallocation or manipulation, leading to data corruption or loss.
- Potential cascading effects might involve denial of service or facilitating further attacks through resource exhaustion.
- Business impact can encompass system instability, compromised data integrity, and potential financial loss due to service downtimes or data breaches.
• Prevention Guidelines:
- Specific code-level fixes include declaring the finalize() method as protected instead of public to restrict access.
- Security best practices involve avoiding reliance on finalize() for critical resource management and instead using try-with-resources or explicit resource management methods.
- Recommended tools and frameworks include static analysis tools that can identify and flag public finalize() method declarations for review and correction.
Technical Details
Likelihood of Exploit: Not specified
Affected Languages: Java
Affected Technologies: Not specified
Vulnerable Code Example
public class MyClass {
// Vulnerable: The finalize() method is declared public,
// which exposes it to external calls, potentially leading to misuse.
public void finalize() throws Throwable {
try {
// Resource cleanup logic
System.out.println("Finalizing...");
} finally {
// It's crucial to call the superclass's finalize method
super.finalize();
}
}
}
How to fix finalize() Method Declared Public?
The finalize() method is meant to be used for cleanup operations before an object is garbage collected. Declaring it as public breaks encapsulation, allowing external entities to invoke it, which can lead to resource mismanagement or security issues.
To address this, the finalize() method should be protected, limiting its accessibility to the class itself and its subclasses. This change ensures that the method is not exposed to external calls, maintaining the integrity of the cleanup process.
Moreover, the use of finalize() is generally discouraged in modern Java development due to its unpredictability and performance implications. Prefer using try-with-resources or java.lang.ref.Cleaner for more reliable resource management.
Fixed Code Example
public class MyClass {
// Fixed: The finalize() method is declared protected, preventing
// external access and ensuring proper encapsulation of cleanup logic.
@Override
protected void finalize() throws Throwable {
try {
// Resource cleanup logic
System.out.println("Finalizing...");
} finally {
// It's important to call the superclass's finalize method to ensure proper cleanup
super.finalize();
}
}
}
Additional Best Practice
For modern Java applications, it is advisable to avoid relying on finalize() due to its limitations and potential pitfalls. Instead, use alternative mechanisms for resource management:
- Try-with-resources: This is ideal for managing resources like file streams, sockets, etc., that implement
AutoCloseable. It ensures that resources are closed promptly and reduces the likelihood of resource leaks. - java.lang.ref.Cleaner: This provides a safer alternative to
finalize()by allowing you to register cleanup actions that are executed when an object becomes unreachable, without the downsides associated withfinalize().