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Sumitomo Mitsui Banking
Tokyo, Japan3 sources
Confirmed:Confirmed by the organisation, a regulator or a securities filing. First reported 5 Nov 2026.
SMBC confirms 227,216 email addresses leaked via vendor
Sumitomo Mitsui Banking Corporation confirmed 227,216 email addresses leaked via the Arara Message vendor. The breach was informed on October 28 and disclosed on November 5.
- Type
- Data breach
- Sector
- Finance
- Records
- 227.2K records confirmed
- First reported
- 5 Nov 2026
- Latest source
- 5 Nov 2026
What to do
- If you have an account, change that password, and anywhere you reused it.
- Turn on two-factor authentication, ideally an authenticator app or passkey, not SMS.
- Expect phishing that uses your real details. Do not click links in messages about this incident; go to the company's site directly.
- If payment cards were involved, watch statements and ask your bank for a new card.
- If government ID or social security numbers were involved, consider a credit freeze.
- If this is a vendor of yours, ask what of your data they held and whether it was in scope.
- Reset any API keys, SSO trusts or shared credentials you have with them.
- Brief your help desk: attackers often impersonate the breached brand next.
Not sure? Ask an assistant with the sources attached, or have a coding agent check your systems.
Check your systems for Sumitomo Mitsui Banking
Sources
3- asianbankingandfinance.net5 Nov 2026asianbankingandfinance.net/financial-technology/news/smbc-data-breach-exposes-227216-customer-email-addresses
- note.com5 Nov 2026note.com/deep_poppy8031/n/n4e533a6e457c
- cybersecurity-jp.com5 Nov 2026cybersecurity-jp.com/news/118150
Confidence 90% that this is real and correctly placed. Locations are city centroids at best. Spotted an error? Report a correction.