The 31-year-old has failed to make an appearance for the Toffees this season and will be hoping for regular first-team minutes under Neil Warnock.
The Boro boss said: “I've known Yannick for many years.
"I asked him if he could help us out until the end of the season and get some fitness in at the same time.
“We can't expect wonders but he's a good lad and he can play different positions for me. He'll be good in the dressing room and it's a big boost for us."