コマツData breach / unauthorized access incident
- Occurred on
- January 1, 2021
- Announced on
- June 16, 2026
- Severity
- AFinancial and HR records — information that easily translates into monetary damage.
- Scale
- 139,000 people
- Main impact
- From around 2021, names, work emails, and other data for approximately 13.9万人 were left accessible. Follow-up reports indicate the exposed attributes were mainly work-related and that viewers were reportedly limited to system users.
- Information involved
- Email addressFull name
- Cause / key point
- A configuration flaw in the user-management mechanism for external-user invitations.
- Industry
- Manufacturing
- Listing / capital
- Listed company東証プライム 6301(小松製作所)
- Sources
- Last updated
- October 20, 2026
Stock price reaction to the disclosure小松製作所 / 東証プライム 6301
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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: Misconfiguration & access-control gaps(Data left readable by anyone)
Read the Misconfiguration & access-control gaps guide and national trends →