Might be normal. A picture would help us.

A pic would really help, it's hard to say without one;).

If the plant feels mushy then you could be dealing with rot, but the cactus could be dehydrated so soft could be confused as mushy;). Cactus at the base can have discoloration and or corking. It's normal.

Here is some pics from the internet of harmless discoloration;). Sometimes it's not pretty and a lot and then on other cactus it's barely noticeable;).

This one looks like the person kept burying and burying as the years went on. I would not suggest doing this;).

It's not the greatest of pictures, but here it is

It can be tricky to tell, many of us have plants that are dead yet they remain in our collections. One pretty good sign is the plant being brown from top to bottom.

Jessi, it looks fine;).