Measurements of the low energy spectrum of Galactic Cosmic Rays ( GCR ) by detectors at or near the Earth are affected by Solar modulation .
To overcome this difficulty , we consider nearby molecular clouds as GCR detectors outside the Solar system .
Using \gamma -ray observations of the clouds by the Fermi telescope we derive the spectrum of GCRs in the clouds from the observed \gamma -ray emission spectrum .
We find that the GCR spectrum has a low energy break with the spectral slope hardening by \Delta \Gamma = 1.1 \pm 0.3 at an energy of E = 9 \pm 3 GeV .
Detection of a low-energy break enables a measurement of GCR energy density in the interstellar space U = 0.9 \pm 0.3 eV/cm ^ { 3 } .