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Unchecked exception classes such as Error and its subclasses are not subject to compile-time checking because it is tedious to account for all exceptional conditions and recovery is generally difficult. However, recovery is usually possible, or a graceful exit that logs the error is at least feasible.

Noncompliant Code Example

This noncompliant code example generates a StackOverflowError as a result of infinite recursion. It exhausts the available stack space and may result in denial of service.

public class StackOverflow {
  public static void main(String[] args) {
    infiniteRun();
    // ...
  }
    
  private static void infiniteRun() {
    infiniteRun();
  }
}

Compliant Solution

This compliant solution shows a try-catch block that can be used to capture java.lang.Error or java.lang.Throwable. A log entry can be made at this point and followed by attempts to free key system resources in the finally block.

public class StackOverflow {
  public static void main(String[] args) {
    try {
      infiniteRun();
    } catch(Throwable t) {
      // Forward to handler
    } finally {
      // Free cache, release resources
    }
    // ...
  }
    
  private static void infiniteRun() {
    infiniteRun();    
  }
}

Note that this solution catches Throwable in an attempt to handle the error and is an exception to guideline EXC14ERR08-J. Catch specific exceptions as opposed to the more general RuntimeException or ExceptionDo not catch NullPointerException or any of its ancestors .

Risk Assessment

Allowing a system error to propagate out of a Java program may result in a denial-of-service attack.

Automated Detection

Automated detection is not feasible.

Related

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Guidelines

Search for vulnerabilities resulting from the violation of this guideline on the CERT website.

Other Languages

This guideline appears in the C++ Secure Coding Standard as : ERR30-CPP. Try to recover gracefully from unexpected errors.

Bibliography

[JLS 2005] Section 11.2, Compile-Time Checking of Exceptions
[Kalinovsky 2004] Chapter 16, Intercepting Control Flow: Intercepting System Errors

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