The origin of the large-scale magnetic fields in the Universe is one of the long-standing problem in cosmology. To discriminate among the different explanations it is crucial measuring the magnetic field in the voids among the galaxies (IGMF, Inter Galactic Magnetic Field). Gamma-rays coming from extragalactic sources can be used to constrain the IGMF due to their interaction with the intergalactic medium. Particularly, strong transients allow to constrain very weak magnetic fields. We used CRPropa 3 to propagate the measured VHE (Very High Energy, E>100 GeV) spectrum from GRB 190114C in the intergalactic medium. We then computed the expected cascade emission in the GeV domain for different IGMF settings and compare it with the Fermi-LAT limits for different exposure times