Report: Aaron Hernandez -- Busted for Being Lookout in Prison Fight

More trouble for convicted murderer Aaron Hernandez -- the ex-NFL star was reportedly busted by prison officials this week for being a lookout (poorly, it appears) in a violent prison fight.

The fight was gang-related, says CNN ... which reports Hernandez agreed to help out an inmate who went into another prisoner's cell and attacked him.

Shocking, considering Hernandez is currently locked up at Souza-Baranowski Correctional Center -- one of the most high-tech maximum security prisons in the country.

Then again, he's already got a life sentence ... so what does he care?!

It's not the first time Hernandez has been involved in a fight behind bars -- TMZ Sports broke the story Hernandez fought an inmate at Bristol County Jail back in 2014.