Builders FirstSource Flex Plan Reports Data Breach Affecting 1,514 Individuals Builders FirstSource Flex Plan, a U.S.-based entity linked to building materials supplier Builders FirstSource Inc., disclosed a data breach impacting 1,514 individuals. The incident was formally reported to the U.S. Department of Health and Human Services (HHS) on February 18, 2026, as it involved protected health information (PHI). Prior to the official disclosure, the threat actor Leaknet claimed responsibility for the breach on December 30, 2025, posting on the dark web and threatening to release the stolen data within 24 hours. Public filings do not specify when the unauthorized access began, how long it persisted, or when the company first detected the breach. While the breach involved PHI, the exact types of exposed data such as medical records, personal identifiers, or financial details have not been publicly detailed. Builders FirstSource Flex Plan has begun notifying affected individuals via mail, outlining the compromised information, the company’s response, and available protective measures. Those who suspect they were impacted but have not received a notification are advised to contact the company directly.