ソフトバンク（回線認証・メッセージ）Data breach / unauthorized access incident
- Occurred on
- January 13, 2026
- Announced on
- January 27, 2026
- Severity
- SCompromise of deep personal data or usable credentials.
- Scale
- Unknown
- Main impact
- A defect in authentication processing caused incidents such as My SoftBank displaying other users' information; disclosed were 2,019 display errors, 2,209 MMS sender replacements, and 2,241 cases of +メッセージ being able to send/receive, among others.
- Information involved
- Phone numberHome addressFull nameDate of birth
- Cause / key point
- A defect in authentication processing.
- Industry
- IT & telecom
- Listing / capital
- Listed company東証プライム 9434(ソフトバンク)
- Last updated
- October 20, 2026
Stock price reaction to the disclosureソフトバンク / 東証プライム 9434
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Written & reviewed
Reviewed byYutaro SasaoFounder & CEO, MediaLeap Inc.
CEO of MediaLeap Inc. Working on both sides of web advertising and web media since 2013; founded the company in May 2025.
Review scope: cross-checking against primary sources (official and government announcements), verifying claims stay within the facts, and checking source attribution。Last reviewed:
Written by:Leak Watch editorial team (AI-assisted drafts verified against sources by the editorial team) · Reviewer profile · Request a correction
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Attack method classification: System defects(Bugs that expose other users' data)
Read the System defects guide and national trends →