KDDI Corporation Email System Breach Affects Up to 14.2 Million Accounts Across Six Japanese ISPs
Japanese telecommunications operator KDDI Corporation disclosed a data breach on June 28, 2026, where threat actors gained access to one of its email systems. The compromise was discovered on June 17, 2026, and was caused by a vulnerability in unnamed third-party software used by KDDI's email system. This breach potentially exposed up to 14.2 million email addresses and passwords, affecting current, former, and inactive customers of KDDI and five other Japanese internet service providers that utilize KDDI's email system.
Signal context
First seen: Jun 28, 2026
Last updated: Jun 29, 2026
Status: Public signal
Key points
- KDDI Corporation disclosed the breach on June 28, 2026.
- Up to 14.2 million email addresses and passwords potentially exposed.
- Breach affected KDDI and five other Japanese ISPs using its email system.
Signal analysis
BetaThis analysis groups the signal by industry, likely incident action and impacted security area. It helps compare this signal with other published signals without treating the labels as final determinations.
Sector: Information
Likely country: Location not provided
Watch internet-facing systems, credential abuse and exploit activity.
- Source type: outside the affected organization
Impact area: Confidentiality
Likely asset: User or customer data
- 33 signals in the same sector
- 97 signals with the same likely impact area
- 1 signal linked to this organization/domain
External sources
Data breach exposes up to 14.2 million email logins at six ISPs - Bleeping Computerhttps://www.bleepingcomputer.com/news/security/data-breach-exposes-up-to-142-million-email-logins-at-six-isps/Public source from bleepingcomputer.com.
KDDI Data Breach Impacts up to 14.2 Million Email Accounts at Six ISPs - Security Affairshttps://securityaffairs.com/194387/data-breach/kddi-data-breach-impacts-up-to-14-2-million-email-accounts-at-six-isps.htmlPublic source from securityaffairs.com.
KDDI Data Breach Impacts up to 14.2 Million Email Accounts at Six ISPs - Security Affairshttps://securityaffairs.co/wordpress/160628/data-breach/kddi-data-breach.htmlPublic source from securityaffairs.co.
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