Unauthorized users exploited a vulnerability in the Defense Manpower Data Center's file-sharing system, accessing unencrypted personnel files from about October 2025 until the flaw was detected on July 16, 2026. The breach may affect roughly 4 million current and former Department of Defense personnel. Exposed information reportedly includes names, dates of birth, contact and demographic data, unencrypted Social Security numbers, and in some cases military occupational specialty or equivalent role codes.
DMDC remediated the vulnerability and restored the affected system, detecting and containing the intrusion in July before notifying individuals on September 18. It offered 12 months of IDX credit-monitoring and identity-restoration services; no malicious use had been reported at publication. The incident has not been attributed, and the exploited vulnerability has not been disclosed, but the combination of identity data and military-role information creates substantial identity-fraud and counterintelligence risk, potentially enabling adversaries to identify and target service members, veterans, and their families.

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DMDC sent breach notifications to affected individuals and offered 12 months of credit monitoring and identity-restoration services through IDX. At the time reported, no malicious use of the exposed data had been identified.
DMDC discovered the vulnerability that enabled the intrusion, patched it, and restored the affected system. The Pentagon reportedly detected and remediated the intrusion after approximately nine months of unauthorized access.
Unauthorized users began accessing a vulnerable DMDC file-sharing server containing unencrypted personnel information. The access reportedly exposed personally identifiable information, including Social Security numbers and military occupational data, affecting potentially about four million people.
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