1. Vulnerability Description

Access to external resources using methods in Java (in/out stream, reader, writer, sockets, http connections, cursors, json parameters, etc.) should be closed after use, otherwise resource leakage may occur.

2. Vulnerability Countermeasure

All finished objects must be closed. Or you can use try-with-resource to make auto close.

3. Example Codd

• Vulnerable code

public static void main(String[] args) {
    FileInputStream fis = null;
    try{
         fis = new FileInputStream("""");
    }catch(IOException e){
        
    }finally {
        // Closing may result in exceptions
        fis.close();
    }
}

• Safe code

public static void main(String[] args) {
    // With try-with-resource enabled, automatically close after try/catch.
    try(FileInputStream fis = new FileInputStream("""")){
         
    }catch(IOException e){

    }
}