Benn, who was expected to make the 53-man roster, broke his collarbone in Saturday's preseason game against the New York Giants and will have surgery Tuesday.
The Jaguars also waived injured offensive tackle Brennan Williams (knee) and injured receiver Damian Copeland (shoulder). If Williams and Copeland clear waivers, they will revert to Jacksonville's injured reserve.
Alexander, who has spent time with Seattle, Dallas and Tampa Bay, worked out for the Jaguars following practice Monday and should help them deal with injuries to backup linebackers LaRoy Reynolds and Khairi Fortt.
Corbin signed with Indianapolis as an undrafted rookie in May, but was waived in July.
Lora has spent time with Minnesota and Detroit.