KDDI Data Breach Impacts up to 14.2 Million Email Accounts at Six ISPs

Security Affairs

June 28, 2026 at 7:11 PM

Actively Exploited

Overview

KDDI Corporation has reported a significant data breach that affects up to 14.2 million email accounts belonging to users of six Japanese internet service providers. The breach occurred due to attackers exploiting a vulnerability in third-party software used by the company. KDDI, one of Japan's largest telecommunications firms, has a large user base, making this breach particularly concerning. Users of the affected email accounts may face risks such as identity theft and unauthorized access to personal information. The incident raises questions about the security of third-party software and the measures companies take to protect sensitive user data.

Key Takeaways

Active Exploitation: This vulnerability is being actively exploited by attackers. Immediate action is recommended.
Affected Systems: Up to 14.2 million email accounts at six Japanese ISPs
Action Required: Users should change their passwords and enable two-factor authentication where available; KDDI is likely working on patches for the vulnerable software.
Timeline: Disclosed on October 2023

Original Article Summary

KDDI Corporation disclosed a breach affecting up to 14.2 million email accounts after attackers exploited a vulnerability in third-party software. KDDI Corporation disclosed a data breach that exposed up to 14.2 million email accounts across six Japanese internet service providers. KDDI Corporation is one of Japan’s largest telecommunications companies. It employs more than 60,000 people […]

Impact

Up to 14.2 million email accounts at six Japanese ISPs

Exploitation Status

This vulnerability is confirmed to be actively exploited by attackers in real-world attacks. Organizations should prioritize patching or implementing workarounds immediately.

Timeline

Disclosed on October 2023

Remediation

Users should change their passwords and enable two-factor authentication where available; KDDI is likely working on patches for the vulnerable software.

Additional Information

This threat intelligence is aggregated from trusted cybersecurity sources. For the most up-to-date information, technical details, and official vendor guidance, please refer to the original article linked below.

Related Topics: This incident relates to Vulnerability, Data Breach.

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