  We investigate the nondegeneracy of higher order Levi forms on weakly
nondegenerate homogeneous $CR$ manifolds. Improving previous results, we prove
that general orbits of real forms in complex flag manifolds have order less or
equal $3$ and the compact ones less or equal~$2$. Finally we construct by Lee
extensions weakly nondegenerate $CR$ vector bundles with arbitrary orders of
nondegeneracy.
