The flat spectrum radio quasar CTA 102 entered an extended period of activity from 2016 to 2017 during which several strong \gamma -ray flares were observed .
Using Fermi large area telescope data a detailed investigation of \gamma -ray \xspace spectra of CTA 102 during the flaring period is performed .
In several periods the \gamma -ray \xspace spectrum is not consistent with a simple power-law , having a hard photon index with an index of \sim ( 1.8 - 2.0 ) that shows a spectral cutoff around an observed photon energy of \sim ( 9 - 16 ) GeV .
The internal \gamma -ray absorption via photon-photon pair production on the broad-line-region-reflected photons can not account for the observed cut-off/break even if the emitting region is very close to the central source .
This cut-off/break is likely due to a similar intrinsic break in the energy distribution of emitting particles .
The origin of the spectral break is investigated through the multiwavelength modeling of the spectral energy distribution , considering a different location for the emitting region .
The observed X-ray and \gamma -ray data is modeled as inverse Compton scattering of synchrotron and/or external photons on the electron population that produce the radio-to-optical emission which allowed to constrain the power-law index and cut-off energy in the electron energy distribution .
The obtained results are discussed in the context of a diffusive acceleration of electrons in the CTA 102 jet .