Two people were wounded in the attack outside the satirical magazine's former office - now home to a television production company - on Friday.
Eight people were arrested, including a man believed to be responsible for the stabbings, which are being investigated by counter-terrorism officers.
Sources close to the investigation said the main suspect - who was detained 500 metres away from the scene - acknowledged carrying out the attack under questioning.
He is alleged to have acted out of anger that Charlie Hebdo had republished the controversial cartoons to mark the start of the trial of alleged accomplices in the terror attack on the magazine five years ago.
Interior minister Gerald Darmanin said the suspect arrived in France three years ago as an unaccompanied minor, apparently from Pakistan.
He had been arrested a month ago for carrying a screwdriver but was not under investigation for Islamic radicalisation, the minister added.
Mr Darmanin conceded that security was lacking on the street where Charlie Hebdo was once headquartered, and ordered special protection for all "symbolic sites" including Jewish sites during the Yom Kippur holiday this weekend.
The two people wounded in Friday's attack were a woman and a man working at the Premieres Lignes documentary production company who had stepped outside for a smoke. Company co-founder Luc Hermann told broadcaster France-Info that they remained in hospital but their condition was "reassuring".
Twelve people were killed when Islamist gunmen Said and Cherif Kouachi stormed the Paris offices and opened fire on 7 January 2015. The magazine is now produced at a secret location.
Prime minister Jean Castex, visiting Paris police headquarters on Saturday, pledged to step up the fight against terrorism, saying: "The enemies of the republic will not win."
Additional reporting by agencies