  High-energy neutrino astronomy is a key pillar of multi-messenger astronomy
and has the potential to also advance fundamental neutrino physics. An accurate
simulation of the neutrino interactions is key in any analysis of neutrino
telescope data. The currently available generator codes of neutrino
interactions use leading order expressions for the differential cross sections
which govern rate and kinematics of the events. These calculations are affected
by well-known large theoretical uncertainties, hence the need of beyond leading
order formalism. Also, a consistent use of modern Parton Density Functions,
which are derived using NLO (or NNLO) frameworks, is required. For this reason
and others, the GENIE event generator of neutrino interactions, which is a
standard tool in the few-GeV energy regime, has so far been stated to be valid
up to only about 1 TeV. The work reported here consists of a high-energy (up to
10$^{10}$ GeV) extension, which will be available in GENIEv4. It interfaces
PYTHIA6 for the hadronization and employs a pragmatic method to assign the
flavour of the struck and outgoing quarks, so that the heavy quark production,
including bottom and top, is also correctly simulated.
