Recent Fermi-LAT observations have revealed the signature of proton acceleration and hadronic emission at GeV energies in various SNRs, possibly due to the interaction with molecular clouds (MCs) in their surroundings. The hadronic interaction is evidenced by a characteristic spectral feature known as the pion-decay bump at energies from hundreds of MeV to a few GeV. We conducted a detailed spectral study with Fermi-LAT of 9 infrared bright SNRs detected by
SPITZER, in which, presumably, particle interaction with the high-density medium favourable for the hadronic emission of gamma-rays occurs. We explain the observed GeV emission in the context of the cosmic ray interaction with the ambient gas, probing the rapid decrease of the maximum energy accompanied by the particle escape, characteristic of old dynamical age, as well as the potential contribution of heavy nuclei, which are in abundance in the circumstellar medium that surrounds core-collapse SNRs. We also report on the potential detection of a few undetected sources in the Fermi-LAT Supernova remnant catalog.