Security experts at Bull are investigating reports that a flaw with its web servers allowed access to confidential customer data.
A spokeswoman for Bull confirmed that an investigation was underway which would establish how deep the problem was.
She said that Bull's customers, which include the Royal Air Force, Barclays and France Telecom, should speak to their local account manager if they are concerned about the problem. She added that the problem originated in France.
Details concerning the problem, which affected a website containing real-time customer access, are still sketchy but it is believed that through human error, confidential information was left without password protection.
The breach is all the more embarrassing for Bull, whose BullSoft division, recently spun off as independent subsidiary Evidian, has a sizeable presence in the security market, particularly within public bodies.
Brian Gladman, technical advisor to the Foundation for Information Policy Research and formerly a technical director with Nato, said the flaw would allow hackers to discover information about what hardware and software was supplied by Bull. This information could then be used to plan attacks, he added.
"The problem is all the more embarrassing because Bull supplies allegedly secure systems," said Gladman.
EE, O2, Vodafone, Three and Airspan open the bidding
Worried about data privacy? Here are several ways to secure your Facebook account
The ICO is seeking an urgent warrant to investigate a major data breach - everything you need to know as the story continues to unfold