  Ever since Penrose and Simpson contradicted Novikov's prediction that an
infalling passenger would emerge into an asymptotically flat universe, there
have been a continued interest in predicting the nature of singularity at the
Cauchy horizon of a Reissner-Nordstrom blackhole. This prediction was first
confirmed by Poisson and Israel using cross-stream of massless particles,
suggesting the phenomenon of mass inflation. Ori however obtained a weaker
singularity using a null shell of radiation. In this work, we consider a
massive scalar field coupled to the Reissner-Nordstrom geometry and analyze the
nature of singularity at the Cauchy horizon. To study the asymptotic behavior
of the mass function and the scalar field near the Cauchy horizon, we
perturbatively solve the coupled dynamical equations emplyoing the Adomian
decomposition method. Our analysis shows that the mass function exhibits a very
rapid and unbounded double-exponential growth, called herein mass
superinflation, which is enormously stronger than previously obtained
singularities. The scalar field is also found to undergo a very strong
blueshift near the Cauchy horizon.
