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Occurring Fact5713Sumitomo Metal Mining Co.,Ltd.Iron and nonferrous metals

Update on Unauthorized Access to the IT Systems of a Philippine Subsidiary

Investigations and recovery efforts concerning the ransomware incident at Philippine subsidiary CBNC have progressed, and the communications networks that had been isolated have been restored. No information leakage or impact on production has been identified. There is no impact on results for the fiscal year ending March 2026, and the impact on results for the fiscal year ending March 2027 is expected to be minor.

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Update on Unauthorized Access to the IT Systems of a Philippine Subsidiary

Subject Entity

Coral Bay Nickel Corporation (CBNC) and 3 of the Company's subsidiaries in the Republic of the Philippines

Target Locations / Products

Certain CBNC servers, the CBNC production plant, and the communications networks of 3 of the Company's subsidiaries in the Republic of the Philippines

Occurrence2 April 2026 (the date on which the encryption of 2 CBNC servers was detected)
Same day
Awareness or receipt of notice2 April 2026 (the date on which the encryption of 2 CBNC servers was detected)
This disclosure05/08/2026
Cause

Damage from a ransomware infection resulting from unauthorized access by a third party

Amount of Impact on Business Performance

There is no impact on results for the fiscal year ending March 2026, and the impact on results for the fiscal year ending March 2027 is considered minor.

Accounting period in which recognized

Fiscal year ending March 2026 (no impact), fiscal year ending March 2027 (the impact is considered minor)

Impact on Earnings Forecast

There is no impact on results for the fiscal year ending March 2026, and the impact on results for the fiscal year ending March 2027 is considered minor.

Company response

Suspended operations

The communications networks of 3 of the Company's subsidiaries in the Republic of the Philippines, including CBNC, had been isolated but have now been restored.

Measures to prevent recurrence

The Company has strengthened measures against unauthorized access across the Group, including CBNC.

Outlook

The Company identified the entry route, investigated the scope of the impact, and restored the systems and data, while also strengthening measures against unauthorized access across the Group, including CBNC. The financial results announcement is scheduled to be disclosed as planned on 11 May 2026.

Event that occurred
ItemDetails
Event nameUpdate on Unauthorized Access to the IT Systems of a Philippine Subsidiary
Date of occurrence2 April 2026 (the date on which the encryption of 2 CBNC servers was detected)
Date recognized / date notice received2 April 2026 (the date on which the encryption of 2 CBNC servers was detected)
Subject EntityCoral Bay Nickel Corporation (CBNC) and 3 of the Company's subsidiaries in the Republic of the Philippines
Target Locations / ProductsCertain CBNC servers, the CBNC production plant, and the communications networks of 3 of the Company's subsidiaries in the Republic of the Philippines
CauseDamage from a ransomware infection resulting from unauthorized access by a third party
Amount of Impact on Business PerformanceThere is no impact on results for the fiscal year ending March 2026, and the impact on results for the fiscal year ending March 2027 is considered minor.
Accounting period in which recognizedFiscal year ending March 2026 (no impact), fiscal year ending March 2027 (the impact is considered minor)
Impact on Earnings ForecastThere is no impact on results for the fiscal year ending March 2026, and the impact on results for the fiscal year ending March 2027 is considered minor.
Suspended operationsThe communications networks of 3 of the Company's subsidiaries in the Republic of the Philippines, including CBNC, had been isolated but have now been restored.
Measures to prevent recurrenceThe Company has strengthened measures against unauthorized access across the Group, including CBNC.
OutlookThe Company identified the entry route, investigated the scope of the impact, and restored the systems and data, while also strengthening measures against unauthorized access across the Group, including CBNC. The financial results announcement is scheduled to be disclosed as planned on 11 May 2026.
Items this document does not state (13)
Type of litigation or proceedingCourt or authorityPlaintiffDefendantDate of filing / date of actionClaim amount / surcharge amountAmount of receivables at risk of non-collection or delayed collectionScheduled resumption dateInvestigation structureDirectors' and officers' liabilityVoting rights ownership percentage before the changeVoting rights ownership percentage after the changePlanned follow-up disclosure

These are items the company does not state in this document. We do not leave them blank, nor fill them in from other sources or by inference.

The reasons the company gives

The company's own explanation, not something inferred from the numbers.

Two CBNC servers were encrypted after being infected with ransomware through unauthorized access by a third party. The Company isolated the affected servers, investigated the entry route and scope of the impact, and restored the systems and data.

How to read this page

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Update on Unauthorized Access to the IT Systems of a Philippine Subsidiary | Sumitomo Metal Mining Co.,Ltd. (5713) timely disclosure | Komori