Cleo attack victim list grows as Hertz confirms customer data stolen – and security experts say it won't be the last

Hertz has confirmed it suffered a data breach as a result of the Cleo zero-day vulnerability in late 2024, with the car rental giant warning that customer data was stolen.

In a statement confirming the incident, the firm said customer data was “acquired by an unauthorized party that we understand exploited zero-day vulnerabilities within Cleo's platform in October 2024 and December 2024”.

“Hertz immediately began analyzing the data to determine the scope of the event and to identify individuals whose personal information may have been impacted,” the statement added.

Customer data exposed in the breach may vary, the company said, but is believed to include customer names, contact information, dates of birth, credit card details, and information pertaining to driver’s licenses.

Similarly, a limited number of customers may have had US social security numbers or government ID information stolen in the breach.

"A very small number of individuals may have had their Social Security or other government identification numbers, passport information, Medicare or Medicaid ID (associated with workers' compensation claims), or injury-related information associated with vehicle accident claims impacted by the event," the company warned.

Hertz said it is yet to observe any “misuse of personal information” linked to the breach, but is offering customers two years of identity monitoring services. The company also advised customers to remain vigilant for potential fraudulent activity.

Hertz the latest to disclose Cleo vulnerability impact

Hertz’ confirmation makes it the latest in a string of companies to have fallen victim to the Cleo breach. First disclosed last year, a vulnerability in the popular managed file transfer (MFT) service was pounced on by the Clop ransomware group.

The threat group initially claimed it had stolen data belonging to more than 60 companies as a result of the zero-day. This list has since grown, and earlier this year Western Alliance Bank confirmed it was among the growing list of victims.

Other confirmed victims include Chicago Public Schools, Champion Home Builders, and WK Kellogg.

Fresh research from ReliaQuest shows the impact of the Cleo breach will continue to grow for enterprises globally. Indeed, analysis by the security firm found the incident fueled a 23% increase in overall ransomware activity between Q4 and Q1 2025.

“Clop’s exploitation of Cleo highlights how weaknesses in systems can ripple across interconnected industries, disrupting supply chains, halting operations, and impacting countless businesses simultaneously,” the firm said in a blog post.

Rebecca Moody, head of data research at Comparitech, echoed this warning, noting that there’s likely to be “many more breach notifications from this exploit” as Clop has since added over 350 victims to its data leak site.

Dray Agha, senior manager of security operations at Huntress, said the incident underlines the “significant risks” posed by vulnerabilities in third-party platforms like Cleo.

“This highlights the importance of maintaining robust vulnerability management programs to identify and address security gaps in software promptly, especially those used for sensitive data transfer.”

Agha added the incident reflects a growing trend of cyber criminals targeting secure file transfer platforms. 2023, for example, saw a number of high-profile organizations impacted by the MOVEit data breach.

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