Patch Now! Cleo Products Actively Exploited in Ransomware Attacks

An actively exploited RCE (Remote Code Execution) with system privileges vulnerability that does not require user-interaction is as bad as it gets from a technical standpoint. When that CVE impacts software widely used by Fortune 500 companies, it is a ticking time bomb. And when advanced persistent threat actors jump on a software vulnerability such as this, remediation needs to become an emergency response effort. Most recently, CVE-2024-50623 (also now tracked as CVE-2024-55956) affecting more than 4,200 users of Cleo’s MFT (Managed File Transfer) software met all these prerequisites for disaster. It has been implicated in active ransomware campaigns affecting several Fortune 500 companies taking center stage in cybersecurity news.

In this cybersecurity alert, we provide a timeline of events related to CVE-2024-50623 and CVE-2024-55956 and associated ransomware campaigns. Even if you are not using an affected product, this will give you valuable insight into the vulnerability lifecycle and the risks of third-party software supply chains. 

CVE-2024-50623 and CVE-2024-55956: a Timeline of Events

The vulnerability lifecycle is complex. You can review our previous article about next-gen vulnerability management for an in depth explanation on how this process happens. In this report, we will provide a timeline for the disclosure and resolution of CVE-2024-50623 and subsequently CVE-2024-55956 as a failed patch attempt from the software vendor Cleo was uncovered and exploited by ransomware operators. Our Greenbone Enterprise Feed includes detection modules for both CVEs [1][2], allowing organizations to identify vulnerable systems and apply emergency remediation. Here is a timeline of events so far:

• October 28, 2024: CVE-2024-50623 (CVSS 10 Critical) affecting several Cleo MFT products was published by the vendor and a patched version 5.8.0.21 was
• November 2024: CVE-2024-50623 was exploited for data exfiltration impacting at least 10 organizations globally including Blue Yonder, a supply chain management service used by Fortune 500 companies.
• December 3, 2024: Security researchers at Huntress identified active exploitation of CVE-2024-50623 capable of bypassing the original patch (version 5.8.0.21).
• December 8, 2024: Huntress observed a significant uptick in the rate of exploitation. This could be explained by the exploit code being sold in a Malware as a Service cyber crime business model or simply that the attackers had finished reconnaissance and launched a widespread campaign for maximum impact.
• December 9, 2024: Active exploitation and proof-of-concept (PoC) exploit code was reported to the software vendor Cleo.
• December 10, 2024: Cleo released a statement acknowledging the exploitability of their products despite security patches and issued additional mitigation guidance.
• December 11, 2024: Wachtowr Labs released a detailed technical report describing how CVE-2024-50623 allows RCE via Arbitrary File Write [CWE-434]. Cleo updated their mitigation guidance and released a subsequent patch (version 5.8.0.24).
• December 13, 2024: A new name, CVE-2024-55956 (CVSS 10 Critical), was issued for tracking this ongoing vulnerability, and CISA added the flaw to its Known Exploited Vulnerabilities (KEV) catalog, flagged for use in ransomware attacks.

Cleo Products Leveraged in Ransomware Attacks

The risk to global business posed by CVE-2024-50623 and CVE-2024-55956 is high. These two CVEs potentially impact more than 4,200 customers of Cleo LexiCom, a desktop-based client for communication with major trading networks, Cleo VLTrader, a server-level solution tailored for mid-enterprise organizations, and Cleo Harmony for large enterprises.

The CVEs have been used as initial access vectors in a recent ransomware campaign. The Termite ransomware operation [1][2] has been implicated in the exploitation of Blue Yonder, a Panasonic subsidiary in November 2024. Blue Yonder is a supply chain management platform used by large tech companies including Microsoft, Lenovo, and Western Digital, and roughly 3,000 other global enterprises across many industries; Bayer, DHL, and 7-Eleven to name a few. Downtime of Blue Yonder’s hosted service caused payroll disruptions for StarBucks. The Clop ransomware group has also claimed responsibility for recent successful ransomware attacks.

In the second stage of some breaches, attackers conducted Active Directory domain enumeration [DS0026], installed web-shells [T1505.003] for persistence [TA0003], and attempted to exfiltrate data [TA0010] from the victim’s network after gaining initial access via RCE. An in-depth technical description of the Termite ransomware’s architecture is also available.

Mitigating CVE-2024-50623 and CVE-2024-55956

Instances of Cleo products version 5.8.0.21 are still vulnerable to cyber attacks. The most recent patch, version 5.8.0.24 is required to mitigate exploitation. All users are urged to apply updates with urgency. Additional mitigation and best practices include disabling the autorun functionality in Cleo products, removing access from the Internet or using firewall rules to restrict access to only authorized IP addresses, and blocking the IP addresses of endpoints implicated in the attacks.

Summary

Cleo Harmony, VLTrader, and LexiCom prior to version 5.8.0.24 are under active exploitation due to critical RCE vulnerabilities (CVE-2024-50623 and CVE-2024-55956). These flaws have been the entry point for successful ransomware attacks against at least 10 organizations and impacting Fortune 500 companies. Greenbone provides detection for affected products and affected users are urged to apply patches and implement mitigation strategies, as attackers will certainly continue to leverage these exploits.