MassMutual Data Breach: SSNs Exposed
By Join The Case · Published December 5, 2025 · Updated December 5, 2025 · 6 min read
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Dapeer Law, P.A., a top-rated class action law firm, is investigating the MassMutual data breach. If you received notice that your information was exposed during this breach, you may be entitled to compensation. It's free to join our investigation to see if we can help you recover.

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MassMutual Data Breach Lawsuit Investigation

A recently filed data-breach notice reveals that personal and medical information belonging to 56 individuals was exposed during an intrusion on a third-party vendor’s systems between October 21, 2024 and January 13, 2025. If you received a letter dated December 11, 2025, you may be entitled to free credit monitoring and potential legal remedies. Contact a qualified data-breach attorney to discuss your rights.

Key Facts

  • Reporting entity : Massachusetts Mutual Life Insurance Company (MassMutual)
  • Number of individuals affected : 56 (reported in Massachusetts)
  • Intrusion window : October 21, 2024 – January 13, 2025
  • Incident discovered : January 15, 2025
  • Consumer notification date : December 11, 2025
  • Free services offered : 24 months of Equifax credit-monitoring and identity-restoration (enroll by February 28, 2026)
  • Toll-free assistance : 800-548-3980
  • Regulatory filing : Massachusetts Attorney General, file #2025-2038
Download Official Breach Notice (PDF)

What Happened

The Massachusetts filing explains that on January 15, 2025, Cigna Healthcare was alerted by a third-party vendor to unauthorized access within the vendor’s systems. The vendor confirmed on September 3, 2025 that client data—including MassMutual records—had been impacted. The breach involved claim overpayment and recovery files handled by the vendor’s Payment Integrity unit. After discovering the issue, the vendor restored operations and alerted law-enforcement authorities.

Information Exposed

The data elements involved vary by person. According to the notice, affected files may have contained:

  • Names
  • Health-care ID numbers
  • Date of service
  • Treatment cost
  • Claim numbers
  • Medical information
  • Social Security numbers (for some individuals)

Steps Taken by MassMutual and Its Vendor

  • Restored vendor systems and operations.
  • Notified law enforcement.
  • Transitioned several services to alternative vendors.
  • Strengthened third-party oversight with periodic security assessments.
  • Provided 24-month Equifax credit-monitoring and identity-restoration at no cost.

Recommended Actions for Impacted Consumers

  1. Enroll in the complimentary Equifax credit-monitoring service before February 28, 2026.
  2. Review account statements and credit reports for unfamiliar activity. Obtain free reports at AnnualCreditReport.com or 1-877-322-8228.
  3. Consider placing a fraud alert or a free security freeze with Equifax, Experian, and TransUnion.
  4. If you spot suspicious activity, file a police report and consult the FTC Identity Theft website or your state Attorney General.
  5. Keep your breach-notification letter and any related documents in a secure place for future legal or insurance claims.

Company Overview

Massachusetts Mutual Life Insurance Company (MassMutual) is a mutual life-insurance company founded in 1851 and headquartered at 1295 State Street, Springfield, Massachusetts, United States. Operating within the financial-services industry, MassMutual employs approximately 10,614 people.

Quick Reference

  • Website: massmutual.com
  • Industry: Financial services
  • Founded: 1851
  • Headquarters: Springfield, MA, USA
  • Employees: 10,614
  • Support line (breach): 800-548-3980
  • Social profiles: LinkedIn  |  X  |  Facebook  |  YouTube  |  Instagram

Frequently Asked Questions

1. I received a data breach letter from MassMutual — what should I do?

Follow the enrollment instructions for the free Equifax credit-monitoring service before February 28, 2026, review your financial accounts, and call 800-548-3980 with any questions.

2. How do I submit a claim related to the MassMutual data breach?

Keep your notification letter and any evidence of fraud, then consult a consumer-privacy attorney or contact MassMutual’s breach-support line (800-548-3980) for guidance.

3. Am I eligible to join a lawsuit against MassMutual?

Eligibility depends on factors such as residence, type of data exposed, and damages. Speak with a data-breach attorney to evaluate your specific situation.

4. What information did the MassMutual breach expose?

Potentially exposed data includes names, health-care ID numbers, dates of service, treatment costs, claim numbers, medical information, and, for some, Social Security numbers.

5. Did MassMutual offer credit monitoring, and for how long?

Yes. The company is offering 24 months of credit monitoring and identity-restoration services through Equifax at no cost.

6. How many people were affected by the MassMutual breach?

The Massachusetts Attorney General filing lists 56 impacted individuals.

7. What caused the MassMutual data breach?

The breach stemmed from unauthorized access to a third-party vendor’s systems that managed claim overpayment and recovery files.

8. How can I get the official breach notice (PDF) for MassMutual?

You can download the full notice directly from the Massachusetts Attorney General’s website using the button above or this link.

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