I am using padding to hide scrollbars but if you scroll to the bottom, you will see that there is additional space. So what is the problem with the CSS ?
.outer {
  width: 300px;
  height: 300px;
  border: 1px solid red;
  overflow: hidden;
}
.inner {
  width: 100%;
  height: 100%;
  overflow: scroll;
  padding: 0 80px 80px 0;
  box-sizing: content-box;
}
.content {
  width: 500px;
  height: 800px;
  background-color: yellow;
  border: 1px solid green;
}<div class='outer'>
  <div class='inner'>
    <div class='content'></div>
  </div>
</div>