  We propose an explanation to the new W mass measurement recently reported by
the CDF collaboration, which is larger than the standard model expectation by
about 7 standard deviations. To alleviate the tensions that are imposed on the
electroweak sector by the new W mass measurement, we carry out an analysis in
the Stueckelberg extended standard model where a new neutral gauge boson
appears which mixes with the two neutral gauge bosons in the electroweak sector
both via the Stueckelberg mass terms and via the gauge invariant
Stueckelberg-Higgs portal interaction and spoils the custodial symmetry at the
tree level so that the simple relation between the W boson mass and the Z boson
mass does not hold. We find that such an extension increases the W boson mass
if the new gauge boson mass is larger than the Z boson mass. We further show
that there exists a significant part of the parameter space in the extended
model which includes the CDF mass anomaly and is consistent with the various
observables at the Z pole and consistent with the ATLAS dilepton limits. The
Stueckelberg $Z'_{\rm St}$ boson, which resolves the CDF W mass anomaly, should
be searchable in future LHC experiments.
