Is a woman's travel without a mahram considered one of the major sins?

A woman who travels alone on a path where she fears for herself, bearing in mind that the basic ruling for a woman traveling without a mahram (definition) is prohibition, even if the journey is short and safe, such as Hajj or Umrah (definition) with women from Tan'im. However, the majority of scholars have permitted a woman to travel for the obligatory Hajj with a trustworthy company of men and women, or women only.