CS.NRE.FUNC.MIGHT

An object reference value from a call to a function that might return null might 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

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
                  public class A {
                      public A foo() {
                          if (flag)
                              return null;
                          return new A();
                      }
  
                      public void var() {
                          A a = foo();
                         if (flag)
                             a.foo();
                     }
 
                     private bool flag;
                 }

Klocwork produces an issue report (CS.NRE.FUNC.MIGHT) at line 11 for variable 'a'. If Variable 'a' is assigned to a value which might be null and which comes from a call to function 'foo' at line 9, it may still be null when it is dereferenced at line 11.

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