The electron binding energies and Kohn-Sham electronic density of states of liquid HCN were calculated by combining Born-Oppenheimer molecular dynamics with electron propagator theory and density functional theory. A modified long-range corrected Perdew-Burke-Ernzerhof exchange-correlation functional (LC-wPBE), where the parameter w was tuned for reproducing the electron binding energies of the HCN monomer and small aggregates was applied in the liquid state calculations. The average HOMO energy of HCN is red-shifted by similar to 0.8 eV relative to its gas-phase value. The vertical electron affinity of liquid HCN is estimated as 1.08 +/- 0.38 eV.