  In previous work, we analyzed the linear and nonlinear stability of static,
spherically symmetric wormhole solutions to Einstein's field equations coupled
to a massless ghost scalar field. Our analysis revealed that all these
solutions are unstable with respect to linear and nonlinear spherically
symmetric perturbations and showed that the perturbation causes the wormholes
to either decay to a Schwarzschild black hole or undergo a rapid expansion.
Here, we consider charged generalization of the previous models by adding to
the gravitational and ghost scalar field an electromagnetic one. We first
derive the most general static, spherically symmetric wormholes in this theory
and show that they give rise to a four-parameter family of solutions. This
family can be naturally divided into subcritical, critical and supercritical
solutions depending on the sign of the sum of the asymptotic masses. Then, we
analyze the linear stability of these solutions. We prove that all subcritical
and all critical solutions possess one exponentially in time growing mode. It
follows that all subcritical and critical wormholes are linearly unstable. In
the supercritical case we provide numerical evidence for the existence of a
similar unstable mode.
