Efforts to combat cyberattacks across the European Union are being undermined by member states' failure to share enough information on the incidents, the European Court of Auditors said on Monday.

The 27-nation bloc was investing more and more in cybersecurity - with €1.4 billion ($1.61 billion) in its current budget - and improving cooperation, according to the court, which reports on how effectively the EU spends money.

But this was not working as well as it should, it added.

Poor information sharing was the "Achilles heel of the entire system", the report said.

"When a serious cyber incident occurs, timely and actionable information is essential. Without it, networks and mechanisms lose much of their added value," it added.

It pointed to a ransomware attack on a technology provider for the aviation industry in September 2025, which disrupted airports in London, Brussels, Berlin, Dublin and other hubs.

None of the affected states notified the EU cybersecurity agency or other members of the incident, the report said.

Individual countries' national security legislation was getting in the way when countries needed to share information about incidents that crossed borders, the court said.

No EU state has reported a "large-scale" cybersecurity incident since 2016, even though that label officially applies to any attack affecting at least two members, it added.

In July, the European Commission referred France, Ireland, the Netherlands and Spain to the EU Court of Justice for failing to adjust their national laws to include EU measures on sharing cybersecurity information.