If you want to create a scrollable area using flexbox, you can use the d-flex flex-column
classes and wrap the content in another div. Then set the inner scrollable div to have an absolute position.
.wrapper {
position: relative;
flex: 1 1 auto;
}
.scroll {
position: absolute;
top: 0; bottom: 0;
overflow-y: auto;
width: 100%;
}
<div class="container">
<div class="row py-4 border border-secondary">
<div class="col-5 py-3 border border-primary">
<p>I need my neighboring column's height to match mine, not the other way around</p>
<div class="border border-warning p-1" style="height: 150px;">
filler content (height: 150px;)
</div>
</div>
<div class="offset-1 col-5 py-3 border border-primary d-flex flex-column position-relative">
<p class="flex-shrink-1">I do not want this column to be scrollable</p>
<div class="border border-warning p-1 wrapper">
<div class="scroll">
<p>I want this section to be scrollable</p>
<p>Filler text, filler text, filler text</p>
<p>Filler text, filler text, filler text</p>
<p>Filler text, filler text, filler text</p>
<p>Filler text, filler text, filler text</p>
<p>Filler text, filler text, filler text</p>
<p>Filler text, filler text, filler text</p>
<p>Filler text, filler text, filler text</p>
<p>Filler text, filler text, filler text</p>
<p>Filler text, filler text, filler text</p>
<p>Filler text, filler text, filler text</p>
</div>
</div>
</div>
</div>
</div>
Link to Live Example
Link to StackBlitz Example