Depends on the country. I applies to CS masters abroad earlier this year with an electrical engineering bachelors. Got into every school in Switzerland and Spain that I applied to - the schools in Switzerland all added mandatory bachelor level modules as a prerequisite. Got rejected by all the schools in Sweden who explicitly stated that it was due to failing to meet the CS bachelors prerequisites. British universities vary in their requirements but they state them explicitly so its easy to find out.

I ultimately decided not to go since I had to move three continents away to Canada around the same time but I've been looking into schools in the US since a US degree is more valuable in Canada than a European one and many seem to be OK with an engineering background.