  The baryon content around local galaxies is observed to be much less than is
needed in Big Bang nucleosynthesis. Simulations indicate that a significant
fraction of these "missing baryons" may be stored in a hot tenuous
circum-galactic medium (CGM) around massive galaxies extending to or even
beyond the virial radius of their dark matter halos. Previous observations in
X-ray and Sunyaev-Zel'dovich (SZ) signal claimed that $\sim(1-50)\%$ of the
expected baryons are stored in a hot CGM within the virial radius. The large
scatter is mainly caused by the very uncertain extrapolation of the hot gas
density profile based on the detection in a small radial range (typically
within 10\%-20\% of the virial radius). Here we report stacking X-ray
observations of six local isolated massive spiral galaxies from the CGM-MASS
sample. We find that the mean density profile can be characterized by a single
power law out to a galactocentric radius of $\approx 200\rm~kpc$ (or
$\approx130\rm~kpc$ above the 1~$\sigma$ background uncertainty), about half
the virial radius of the dark matter halo. We can now estimate that the hot CGM
within the virial radius accounts for $(8\pm4)\%$ of the baryonic mass expected
for the halos. Including the stars, the baryon fraction is $(27\pm16)\%$, or
$(39\pm20)\%$ by assuming a flattened density profile at $r\gtrsim130\rm~kpc$.
We conclude that the hot baryons within the virial radius of massive galaxy
halos are insufficient to explain the "missing baryons".
