... you have a flaw in your code ...

Not really. It's doing exactly what I thought the challenge required.

Then I strongly suggest that you completely re-word the text of your challenge. Something along the lines of:

The mystery word has exactly 2 unique letters in common with 'bumps'

As the rules stand, with the details spread all over the place like that, it is very misinterpretable.

As for my "code", it was originally a hand-coded single regex applied to all the 5 characters words in my words file.

I had just finished writing a script to generate the regex from command line input of the form:

P:\test>421692-1 5 bumps:2 seams:2 domes:3 shake:3 pokes:3 dukes:3
8
dukes
house
krems
makes
pokes
smoke
spade
spoke
[download]

When I read your reply that I was misinterpreting your spec. I'll have to take a look and see if it is adaptable to my new understanding of the rules.