CMS Data Breach History

This page tracks the CMS data breach history and cybersecurity incidents affecting CMS (United States). BreachHistory currently indexes 1 publicly disclosed or catalogued incident spanning 2018, with approximately 94 thousand records reported as exposed across all indexed events. These totals may include overlapping datasets or third-party estimates and should not be interpreted as unique affected users.

The CMS breach timeline includes major data breaches, cyber attacks, data leaks, credential exposures, API abuse, and other security incidents. Each incident provides details on the estimated records exposed, attack method, affected data types, and supporting public sources. Currently, 0 incidents are company-confirmed.

Largest CMS Data Breaches

The largest indexed incidents include the 2018 — CMS: CMS states that no protected health info, banking…. Record counts originating from threat actors or leak sites should be treated as estimates unless confirmed by CMS or a regulator. Below is the list of large data breaches:

• 2018 2018 — CMS: CMS states that no protected health info, banking… — about 93.7K records exposed · Catalogued incident

What Information Was Exposed?

Depending on the incident, exposed data may include email addresses, passwords, phone numbers, names, profile information, account identifiers, and other personal information (PII). The exact data varies between incidents, so review each breach page before assuming your information was affected.

CMS Data Breach 2026

At the time of this update, no CMS data breach has been catalogued for 2026. New incidents are added as official disclosures, regulatory filings, or credible cybersecurity reports become available.

What To Do If You Were Affected

If you believe your account may have been involved in a CMS data breach, change any reused passwords, enable multi-factor authentication (MFA), monitor your account for suspicious activity, and be cautious of phishing emails or fake breach notifications.

This CMS breach history is maintained by BreachHistory using public disclosures, regulatory filings, security research, and clearly labelled third-party claims. For the complete breach timeline, records exposed, incident details, and AI Breach Risk Score, explore the sections on this page.