A critical vulnerability affecting Cleo’s file transfer software, including LexiCom, VLTransfer, and Harmony, is actively being exploited by threat actors. Tracked as CVE-2024-50623, the issue stems from an unrestricted file upload feature, which allows attackers to execute arbitrary code on vulnerable systems without authentication. Cybersecurity firm Huntress reported evidence of widespread exploitation on December 3, 2024, with attackers leveraging the flaw to install malware on Cleo-managed servers, including the drop of XML files that initiate a PowerShell command to download a next-stage Java Archive (JAR) file from a remote server.
The vulnerability has impacted at least 10 organizations across various sectors, including consumer products, logistics, and food supply chains. The exploitation often begins when files are placed in the “autorun” sub-directory of Cleo’s software, where they are immediately read and executed. The surge in exploitation activity was observed around December 8, 2024, highlighting the urgency of addressing the issue. As of now, a patch for CVE-2024-50623 has been released, but it has not fully mitigated the underlying flaw, prompting further concerns.
In addition to this vulnerability, Cleo has issued a separate advisory warning of a “malicious hosts” vulnerability that could also lead to remote code execution. While patches for these issues are expected soon, the urgency is clear, as threat actors continue to exploit the vulnerabilities. Notably, cybersecurity experts have tied these attacks to ransomware groups, including Termite, which has previously targeted similar file transfer tools, hinting at a rise in sophisticated ransomware activity. The Termite group is believed to be using a modified version of Babuk ransomware to encrypt compromised files.
With over 1,300 exposed Cleo instances detected online, primarily in the United States, organizations are urged to ensure their software is updated and properly secured. The continued exploitation of this vulnerability underscores the critical need for proactive security measures, including limiting internet exposure for Cleo-managed systems. As the investigation unfolds, it’s important for businesses to remain vigilant and act quickly to mitigate potential damage from this ongoing threat.
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