  We consider virtual electroweak corrections to the form factors for massless
chiral fermions coupling to an SU(2)xU(1) singlet gauge boson in the asymptotic
region $s\gg M_W^2$, where the invariant mass $s$ of the external gauge boson
is much higher than the weak-boson mass scale. Using the sector-decomposition
method we compute mass singularities, which arise as logarithms of $s/M_W^2$
and $1/\epsilon$ poles in $D=4-2\epsilon$ dimensions, to one- and two-loop
next-to-leading logarithmic accuracy. In this approximation we include all
contributions of order $\alpha^l \epsilon^{k} log^{j+k}(s/M_W^2)$, with $l=1,2$
and $j=2l,2l-1$. We find that the electroweak two-loop leading- and
next-to-leading-logarithmic mass singularities can be written in a form that
corresponds to a generalization of Catani's formula for massless QCD.
