CS.NRE.CHECK.MUST

An object reference value that is positively checked for null will be dereferenced either explicitly, or through a call to a function that can dereference it, without checking for null.

Vulnerability and risk

Dereferencing a null object reference is a critical runtime problem that will crash the application on some operating systems and throw a runtime exception on others.

Example 1

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                  public class A {
                      public void foo() {
                          A a = new A();
                          if (a == null)
                              a.foo();
                      }
                  }

Klocwork produces an issue report (CS.NRE.CHECK.MUST) at line 5 for variable 'a'. Variable 'a' is compared with null value at line 4, and therefore can be expected to be null when it is dereferenced at line 5.

External guidance

• CWE-476: NULL Pointer Dereference

Security training

Application security training materials provided by Secure Code Warrior.

• Null Dereference Training Video - Test your skills with a training example