The breach was caused by threat actors exploiting a vulnerability in third-party software used by KDDI Corporation's email systems, leading to unauthorized access. The compromise potentially exposed the email addresses and passwords of up to 14.2 million customers across KDDI and five other Japanese ISPs. Customers are advised to reset passwords and enable two-factor authentication, while organizations should review their use of the implicated third-party software.
Breach KDDI discloses data breach affecting up to 14.2 million customers June 29, 2026 Share By SC Staff (Adobe Stock) Japanese telecommunications operator KDDI Corporation has disclosed a significant data breach impacting its email systems, which are also used by five other internet service providers in the country. The company discovered the compromise on June 17 and has since implemented defensive measures, based on information published by Bleeping Computer. The breach occurred when threat actors exploited a vulnerability in third-party software used by KDDI. This unauthorized access may have exposed the email addresses and passwords of up to 14.2 million customers, including current and former users. While some passwords were stored in hashed or encrypted forms, the exact extent of plaintext password exposure remains unclear. The incident affected several major ISPs in Japan: STNet, Inc., JCOM Co., Ltd., Chubu Telecommunications C., Inc., NIFTY Corporation, and BIGLOBE Inc. KDDI has notified Japanese authorities and is working with the affected ISPs to enhance security. Customers are advised to reset their passwords and enable two-factor authentication if available. Source: Bleeping Computer SC Staff Related Breach Xsolis breach exposes personal and health data of 1.4 million people SC Staff June 23, 2026 The security incident, which occurred on January 20, 2026, allowed an unauthorized actor to acquire files containing sensitive information. Breach Tata Electronics confirms data breach after sensitive files appear online SC Staff June 23, 2026 The breach was revealed after a hacker forum listed over 630 GB of data, reportedly containing more than 204,300 files. Breach Novo Nordisk discloses data breach affecting patient and healthcare professional information SC Staff June 12, 2026 Attackers gained access to Novo Nordisk's internal IT systems, copying non-public data without authorization. Get daily email updates SC Media's daily must-read of the most current and pressing daily news Business Email By clicking the Subscribe button below, you agree to SC Media Terms of Use and Privacy Policy . Subscribe Related Terms Attack Vector You can skip this ad in 5 seconds