CS.NRE.GEN.CALL.MUST

An object reference from local assignment of a null-constant or from a call to a function that will return null will be passed 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 abc() {}
     public void foo(A a) {
      if (flag)
        return;
      a.abc();
     }
  
     public void var() {
     A a = null;
     foo(a);
    }
 
    private bool flag;
 }

Klocwork produces an issue report (CS.NRE.GEN.CALL.MUST) at line 11 for variable 'a'. Variable 'a' is explicitly assigned to null value at line 10 and will be passed as argument 1 to function 'foo' at line 11, which may dereference it.

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