Rapid 7 - Widespread exploitation of Cleo file transfer software (CVE-2024-50623)

On Monday, December 9, multiple security firms began privately circulating reports of in-the-wild exploitation targeting Cleo file transfer software. Late the evening of December 9, security firm Huntress published a blog on active exploitation of three different Cleo products (docs):

• Cleo VLTrader, a server-side solution for “mid-enterprise organizations”
• Cleo Harmony, which provides file transfer capabilities for “large enterprises”
• Cleo LexiCom, a desktop-based client for communication with major trading networks  

Huntress’s blog says the exploitation they’re seeing across Cleo products results from an insufficient patch for CVE-2024-50623, a vulnerability disclosed in Cleo VLTrader, Cleo Harmony, and Cleo LexiCom in October 2024. Cleo indicated that the vulnerability was fixed in version 5.8.0.21 of all three solutions, but according to Huntress, 5.8.0.21 remains vulnerable to exploitation. CVE-2024-50623 is a cross-site scripting issue (CWE-79) that allows for unauthenticated remote code execution on target systems.

As of December 10, Rapid7 MDR has confirmed successful exploitation of this issue in customer environments; similar to Huntress, our team has observed enumeration and post-exploitation activity and is investigating multiple incidents.

File transfer software continues to be a target for adversaries, and for financially motivated threat actors in particular. Rapid7 recommends taking emergency action to mitigate risk related to this threat.

Mitigation guidance

The following products and versions are believed to be vulnerable to CVE-2024-50623. If CVE-2024-50623 is indeed the sole root cause of observed threat activity, it should be considered unpatched. The information below contradicts previous vendor guidance, which indicated that 5.8.0.21.

• Cleo Harmony before and including version 5.8.0.21
• Cleo VLTrader before and including version 5.8.0.21
• Cleo LexiCom before and including version 5.8.0.21

According to Huntress, “Cleo is preparing a new CVE designation and expects a new patch to be released mid-week.”

In the absence of an effective patch for CVE-2024-50623 (and any other CVEs that may be assigned to this exploit), Cleo customers should remove affected products from the public internet, ensuring they are behind a firewall. Per Huntress’s investigation, disabling Cleo’s Autorun Directory, which allows command files to be automatically processed, may also prevent the latter part of the attack chain from being executed.

Huntress’s blog has several descriptions of post-exploitation activity, including attack chain artifacts, commands run, and files dropped for persistence. Rapid7 recommends that affected customers review these indicators and investigate their environments for suspicious activity dating back to at least December 3, 2024.

Rapid7 customers

InsightVM and Nexpose customers will be able to assess their exposure to CVE-2024-50623 on Windows with an authenticated vulnerability check expected to be available in today’s (Tuesday, December 10) content release. Please note that content releases are typically available late in the evening ET on Patch Tuesday.

InsightIDR and Managed Detection and Response customers have existing detection coverage through Rapid7's expansive library of detection rules. Rapid7 recommends installing the Insight Agent on all applicable hosts to ensure visibility into suspicious processes and proper detection coverage. Below is a non-exhaustive list of rules deployed and alerting on behavior related to this threat:

• Suspicious Process - XORed Data in PowerShell
• Suspicious Process - PowerShell System.Net.Sockets.TcpClient
• Attacker Behavior - Possible Cleo MFT Exploitation 2024
• Attacker Tool - PowerShell -noni -ep -nop Flags
• Attacker Behavior - Obfuscated Powershell Script Containing -noni -ep -nop Flags
• Suspicious Process - Powershell Invoke-WebRequest

from Rapid7 Cybersecurity Blog https://blog.rapid7.com/2024/12/10/etr-widespread-exploitation-of-cleo-file-transfer-software-cve-2024-50623/