Cloud computing giant Rackspace has confirmed hackers accessed customer data during last month’s ransomware attack.

The attack, which Rackspace first confirmed on December 6, impacted the company’s hosted Exchange email environment, forcing the web giant to shut down the hosted email service following the incident. At the time, Rackspace said it was unaware “what, if any, data was affected.”

In its latest incident response update published on Friday, Rackspace admitted that the hackers gained access to the personal data of 27 customers. Rackspace said the hackers accessed PST files, typically used to store backup and archived copies of emails, calendar events and contacts from Exchange accounts and email inboxes.

Rackspace said about 30,000 customers used its hosted Exchange service — which it will now discontinue — at the time of the ransomware attack.

“We have already communicated our findings to these customers proactively, and importantly, according to Crowdstrike, there is no evidence that the threat actor actually viewed, obtained, misused, or disseminated any of the 27 Hosted Exchange customers’ emails or data in the PSTs in any way,” said Rackspace. The company added that customers that haven’t been contacted directly can “be assured” that their data was not accessed by attackers.

Rackspace attributed the breach to the Play ransomware group, a relatively new gang that recently claimed attacks on the Belgian port city of Antwerp and the H-Hotels hospitality chain. Rackspace’s stolen data is not currently listed on the ransomware group’s leak site, and it’s unclear if Rackspace has paid a ransom demand.

According to the incident report update, Play threat actors gained access to Rackspace’s networks by exploiting CVE-2022-41080, a zero-day flaw patched by Microsoft in November that has been linked to previous ransomware incidents.