Cleo MFT Vulnerability CVE-2024

CVE-2024-50623 is an unrestricted file upload and download flaw (CWE-434) in Cleo's managed file transfer products — Harmony, VLTrader, and LexiCom — before version 5.8.0.21. It is reachable over the network with no authentication or user interaction (CVSS 9.8, AV:N/AC:L/PR:N), letting an attacker send crafted requests that upload arbitrary files to the server. The unrestricted upload leads to remote code execution, giving the attacker full control of the host for staging, data theft, or ransomware, while the download capability risks exposure of business files the server moves with trading partners. Any organization running these products is affected, and managed file transfer servers are typically internet-facing and handle sensitive B2B data. Exploitation is confirmed in the wild: CISA added it to the KEV catalog on 2024-12-13 with ransomware use noted, EPSS assigns a 98.6% probability of exploitation within 30 days, and the Clop ransomware gang has claimed dozens of breaches (some disputed), including a confirmed breach at WK Kellogg.

Do: Upgrade Harmony, VLTrader, and LexiCom to 5.8.0.21 or later per vendor instructions; if upgrading is not possible, apply vendor mitigations or discontinue use of the product, as CISA's KEV entry requires. Prioritize internet-exposed instances, hunt for indicators of compromise (unexpected file writes and execution on the transfer host, new accounts, suspicious outbound connections), and restrict the service to trusted partner networks. Given known ransomware use by Clop, any suspected compromise should trigger checks for lateral movement and staged exfiltration of transferred files.

CVE-2024-55956 is an unauthenticated command-execution flaw (CWE-77) in Cleo's managed file transfer products: by default the Autorun directory automatically imports and runs files, so an unauthenticated attacker can import Bash or PowerShell commands that execute on the host. It is triggered over the network with no authentication and no user interaction (CVSS 3.1 score 9.8), by sending crafted import requests to a vulnerable Cleo server. Successful exploitation yields arbitrary command execution on the server, enabling data theft, lateral movement, and ransomware deployment. Any organization running Cleo Harmony, VLTrader, or LexiCom before 5.8.0.24 is affected — typically enterprises using these servers for EDI and partner file exchange. The flaw is actively exploited in the wild: it was added to CISA KEV on 2024-12-17 with known ransomware use (widely attributed to Cl0p), EPSS is 94% (top percentile), and confirmed downstream breaches such as WK Kellogg's have been tied to it.

Do: Upgrade all Cleo Harmony, VLTrader, and LexiCom instances to 5.8.0.24 or later immediately, per the CISA KEV required action to apply vendor mitigations or discontinue use. If patching is delayed, restrict or remove internet exposure of the server. Because exploitation is confirmed and ransomware-linked, inspect the Autorun directory for unexpected imported files, review application logs for executed commands, and hunt for signs of data exfiltration or staging.