Bio-based hardeners that are not amine or anhydride based are of particular interest to avoid associated health concerns. In the present study, a recently developed furfural-based cross-linker bearing a semi-rigid cyclobutane moiety is investigated for its capacity to cross-link epoxidized linseed oil, resulting in a wholly bio-based thermoset. The kinetics of the curing process are elucidated, as well as the mechanical properties of the resulting material. The cured thermoset displayed particularly high tensile strength and a high glass transition for a flexible triglyceride-based network, exceeding that of many previously published di-acid thermosets.