Which chainring? Shimano M785
You are correct that the 42x26 is telling you that the large ring has 42 teeth (and the small 26).

I did a search on "M785 replacement chainring" and found a number of sources (but nothing a Chain Reaction). Looking at what I found it appears that the options for the large ring are 38 and 40 teeth. So…

Either Shimano has changed the specs on the M785 and the 42 tooth ring is no longer available, or there is s typo on the Cube site. I'd say it's worth looking at your bike to see if the tooth count is stamped on the chainring or, failing that, count the teeth.

If it is a 42 tooth ring (and you want the higher gears) it might be worth going to your LBS to see if they can order the 42 tooth ring, or else look for NOS (new old stock) rings on places like Ebay.