A Pentagon data breach has exposed personal information belonging to more than 3 million people. According to notification letters, unauthorized users accessed unencrypted files through a Defense Manpower Data Center (DMDC) file-sharing vulnerability for months.
Unauthorized Access Began in October 2025
DMDC discovered the breach on July 16, 2026. However, its notification letters say a small number of unauthorized users had accessed files since October 2025.
The agency says it immediately patched the vulnerability and restored the file-sharing system after discovering the problem.
According to Pentagon figures that CNN reported, the incident affected approximately 2.8 million living individuals. In addition, it exposed records concerning 294,000 deceased former defense personnel or their dependents.
Together, those figures put the total above 3 million people.
Exposed Files Contained Social Security Numbers
The Pentagon data breach involved files containing unencrypted personally identifiable information.
According to the notification, the affected data included Social Security numbers alongside one or more additional identifiers:
- Names
- Dates of birth
- Contact information
- Sex
- Race
- Military personnel details, such as occupational specialties
However, the notification does not indicate that every affected person had every listed type of information exposed.
DMDC Maintains Millions of Personnel Records
DMDC manages databases covering defense personnel, manpower, training and related areas.
According to its website, the agency oversaw more than 60 million personnel records as of 2024. Those records covered military members, civilian employees, contractors, family members, retirees and veterans.
That broader database figure describes the agency’s responsibilities. It does not represent the number of people affected by this incident.
Agency Offers Credit Monitoring After Breach
DMDC says it is assessing and strengthening its systems following its privacy and cybersecurity response.
Meanwhile, the department says it has no indication that anyone has misused the accessed information. That statement does not establish whether misuse could emerge later.
The agency has also offered affected individuals 12 months of free credit monitoring.
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