Your question is pretty challenging because I'm not sure if there is any (internationally) valid canon of (even undergraduate) CS studies.

Furthermore I doubt that even 10% of the colleagues I met on job (or monks I met here - sorry ) had more than a basic grasp of what I learned in the first 2 years at uni.*

And some things I already studied in high-school like combinatorics, algebra and probability theory are only part of undergraduate studies in other countries.

Saying so, I don't think it was the content which mattered, but rather the methodology to cleanly define a problem, to find proper names for the "things" involved and the ability to look-up available research /tutorials on the field.

In the end I have to look-up the details again after years not using them.

But at least I know where to look and that they exist.

Keep in mind that things are evolving far too fast in CS to still be valid after a few years.

Now I could start dropping names like

• Graph Theory,
• Dijkstra-Algorithm,
• complexity and big O notation,
• coding theory,
• information redundancy & Shannon
• proving algorithms,
• Boolean algebra and simplifying gate logic
• other fields of Discrete_mathematics
• ... and so on

... which might have been essential in my uni but but not in the next one.

(My professors where all from two groups, either a degree in Math or Electrical Engineering. CS as a faculty was too young for "real" CS profs)

So my advice is

• don't be too shy
• don't expect that your interviewer knows much about CS
• get an overview of the concepts/names of the main topics in CS to avoid a blank stare when asked
• browse thru different open-course-ware offers for undergraduates
• learn how to look up things when needed (WP, google, ...)

Finally: a little search led me to this MIT stuff https://ocw.mit.edu/courses/electrical-engineering-and-computer-science/, but there are certainly also other sources.

I'd browse thru it and pick the stuff that motivate you.

One major obstacle though ... they require you to learn some Python! ;-P

HTH! :)

update

*) which is also biased b/c my profs used to push their research fields. And being at a technical universities meant plenty of research fields.