A cybersecurity breach at the Pentagon exposed personal information of nearly 3 million living people, including US military personnel, civilian employees, contractors and veterans.

A US defence official confirmed that an information system operated by the Defense Manpower Data Center (DMDC) was accessed without authorisation between October 2025 and July 2026, according to ABC News.

The breach affected about 2.76 million living people and records of another 294,000 deceased individuals, reports said.

The DMDC is one of the Pentagon’s main repositories of personnel information, holding records on active-duty and reserve service members, civilian employees, contractors, veterans and others. The centre maintains records on more than 60 million individuals.

The compromised information included Social Security numbers and details about military and civilian job positions. In some cases, the accessed records reportedly contained military personnel’s occupational specialties.

The exposed data was not encrypted, according to a notification letter reviewed by CNN.

Defence officials said the vulnerability was addressed after the unauthorised access was discovered. They have so far found no evidence that the compromised information has been misused.

The inclusion of military job details has raised additional security concerns, as such information could potentially be combined with other datasets to identify or profile personnel.

The identity of those responsible for the breach remains unknown, and no hacking group has publicly claimed responsibility.

The incident comes amid a separate reported breach involving FBI employee data, highlighting growing concerns over the security of sensitive personnel information held by US government agencies.