  This study investigates the precision measurement of the CKM matrix element
$|V_{cb}|$ through semileptonic $WW$ events at future Higgs factories, $i.e.$,
FCC-ee, ILC, C$^3$, and CEPC. We use full detector simulation to generate the
$WW \to \ell \nu cb$ signal events and various backgrounds at $\sqrt{s} = 240$
GeV with unpolarized beams. The relative statistical uncertainties are
projected to be 0.91\% for the muon channel and 1.2\% for the electron channel,
assuming a baseline integrated luminosity of 5 ab$^{-1}$. The sensitivities at
other Higgs factory scenarios are also projected. Possible contributors to
systematic uncertainties are discussed, with the most prominent one being the
systematics of flavor-tagging and mistagging rates. Combining with $WW$
threshold runs, the relative systematic uncertainty can be further reduced.
