  We calculate new constraints on extra neutrino interactions via light Abelian
vector bosons, where the boson mass arises from Stuckelberg mechanism. We use
the requirement that $Z$, $W$, and kaon decays, as well as electron-neutrino
scattering, are not altered by the new interactions beyond what is allowed by
experimental uncertainties. These constraints are strong and apply to
neutrinophilic dark matter, where interactions of neutrinos and dark matter via
a new gauge boson are important. In particular, we show that models where
neutrino interactions are needed to solve the small-scale structure problems in
the $\Lambda$CDM cosmology are constrained.
