  Exact low-temperature asymptotic behavior of boundary contribution to
specific heat and susceptibility in the one-dimensional spin-1/2 XXZ model with
exchange anisotropy 1/2 < \Delta \le 1 is analytically obtained using the
Abelian bosonization method. The boundary spin susceptibility is divergent in
the low-temperature limit. This singular behavior is caused by the first-order
contribution of a bulk leading irrelevant operator to boundary free energy. The
result is confirmed by numerical simulations of finite-size systems. The
anomalous boundary contributions in the spin isotropic case are universal.
