The blackout lasted just over an hour and started just before midnight on 17 December.
The cyber-security company Information Systems Security Partners (ISSP) has linked the incident to a hack and blackout in 2015 that affected 225,000.
It also said a series of other recent attacks in Ukraine were connected.
The 2016 power cut had amounted to a loss of about one-fifth of Kiev's power consumption at that time of night, national energy company Ukrenergo said at the time.
