  We consider quantum backreaction of the quantized scalar field with an
arbitrary mass and curvature coupling on ultraextremal horizons. The problem is
distinguished in that (in contrast to non-extremal or extremal black holes) the
WKB approximation remains valid near $r_{+}$ (which is the radius of the
horizon) even in the massless limit. We examine the behavior of the
stress-energy tensor of the quantized field near $r_{+}$ and show that
quantum-corrected objects under discussion do exist. In the limit of the large
mass our results agree with previous ones known in literature.
