McAleny suffered a fracture to his right tibia during the Bees' League One match against Walsall on Saturday.
Everton Under-21s manager Alan Stubbs told evertonfc.com: "It's bitterly disappointing for Conor and I really feel for him. He was doing well down there, getting some game time and Brentford enjoyed having him. But things like this can happen and we'll be here to help him back to full fitness."
For the big stories and the banter follow us on Twitter: @tribalfootball