The case is being investigated but the government's work is continuing as normal, Norwegian authorities said.
Norwegian authorities reported a cyber attack of unknown origin against 12 government ministries on Monday.
A police investigation into the incident has been opened and the Norwegian Data Protection Authority had been notified of the problem.
"We have uncovered a previously unknown vulnerability in the software of one of our suppliers," said Erik Hope, director of the Norwegian ministries' security and service organisation, in a press statement.
"This vulnerability has been exploited by an unknown actor. We have now closed this vulnerability. It is too early to say anything about who is behind it and the scale of the attack. Our investigations and the police's investigation will be able to provide more answers".
Authorities said the government's work was continuing as normal but that in the 12 ministries impacted by the attack, workers did not have access to common mobile services including e-mail.
The Prime Minister's services, defence foreign affairs and justice ministries were not impacted as they have their own separate platforms.
In 2020 and 2021, the Norwegian Parliament was targeted by computer attacks, at least one of which was attributed to Russian hackers.