This was reported on February, 26.
According to the press secretary of the channel, the picture of Putin was accidentally uploaded “due to a failure of the video server during the breaking news broadcast.” He added that the image was prepared for the next story.
The photo of the Russian president appeared during a broadcast immediately after the photo of the ISIS militant Jihadi John, taken from the video of one of the executions. You can watch an excerpt from the video YouTube.
Recently, CNN has had frequent mishaps. Earlier in February, the channel mistakenly “annexed” Ukraine to Russia. During the news story on the events in Europe, CNN showed a map on which Russia and Ukraine were painted the same color and over the whole territory there was a Russian flag.