Sony Network Communications’ official FAQ says it confirmed on 23 October 2026 that the So-net member database had been accessed from outside, that registered customers’ personal data had leaked as a result, and that it then took the server offline and immediately blocked the source, with no further leak confirmed after that [2]. The leaked So-net and plala (S-course) member records total up to about 2.586 million, including names, phone numbers, primary and contact email addresses, user IDs, dates of birth, connection IDs and sex; the FAQ also lists about 54,000 mail addresses and mail passwords for Mail Service (G), A-Box, VAIO Mail and PostPet, 16 bank-account records (no PINs) and 7 password-reset notices, and says the company does not hold credit-card data so no card data leaked [2]. It has forced a mail-password change on the affected mail services, so those users must follow the official restart steps to reset the password before they can use the service again; it also asked all customers not to respond to unexpected emails, SMS or calls, and not to open links or attachments in those messages [2].
HighMonitoringOfficially confirmed
So-net member database breach exposes up to about 2.59 million records; some mail passwords must be reset
1 min read
- Disclosed
- Oct 29, 2026
- Occurred
- Oct 23, 2026
- Published
- Nov 12, 2026
- Last updated
- Nov 12, 2026
- Scale
- 2,586,000 records[2]
- CVSS basis
- Our assessment
On this page
30-second summary
What happened
Who is affected
Current So-net and plala (S-course) members, and former members still in the retention period; member records total up to about 2.586 million, plus about 54,000 mail passwords and other items [2]
What to do nowOur advice
- If you use Mail Service (G), A-Box, VAIO Mail or PostPet, follow the official restart steps to reset that mail password, and also update mail-software settings [2].
- Do not respond to unexpected emails, SMS or calls, and do not open links or attachments in those messages [2].
- For other questions, see the official FAQ or call the So-net hotline 0120-36-8887 (weekdays and Saturdays 10:00–18:00) [2].
Timeline
Technical details
Remediation
References
Official / primary2
- [1]ソニーネットワークコミュニケーションズ株式会社2026-10-27Accessed 2026-11-12Snapshot 2026-11-12 sha256 5a059a76077f
“項目２―②に該当するお客様は、メールアドレスパスワードの再設定を行って頂く必要がございます”
- [2]ソニーネットワークコミュニケーションズ株式会社2026-10-29Accessed 2026-11-12Snapshot 2026-11-12 sha256 2277576d4a96
“最大 258.6 万件です”
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