Aesto Health has reported a data breach affecting 9.54 million individuals to HHS, one of the largest healthcare breaches disclosed in 2026.
Aesto, which provides data migration, EHR exchange and legacy data archiving services to healthcare providers, detected unauthorized activity within a portion of its Amazon Web Services infrastructure on Dec. 18, 2025, according to a June company notice. After an extensive forensic investigation and manual document review, the company confirmed on May 26 that an unauthorized actor may have accessed or acquired data between Dec. 2 and Dec. 18, 2025.
The exposed information varied by individual and included full names, dates of birth, medical information, driver’s license numbers, financial account numbers, health insurance information, taxpayer identification numbers, other government identification numbers and Social Security numbers.
Aesto began notifying its covered entity clients on June 26. As a business associate, Aesto is not itself the covered entity; the affected health systems and practices bear ultimate responsibility for notifying impacted patients, and some have already done so independently. Aesto reported the breach to HHS on July 31, and the agency posted the figure Aug. 31.
Aesto said it has no evidence of identity theft or financial fraud connected to the incident. The company has established a toll-free response line for questions related to the breach.
The incident underscores the exposure health systems face through third-party vendors that store and migrate patient data, a recurring theme in 2026’s data breach landscape.
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