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CriticalCISA KEVExploited in the wildPublic exploit

Unauthenticated unrestricted file upload/download leading to RCE in Cleo Harmony, VLTrader, and LexiCom

IdentifiersCVE-2024-50623CWE-434· Unrestricted Upload of File with…

CVE-2024-50623 affects Cleo Harmony, VLTrader, and LexiCom before version 5.8.0.21. The vulnerability is described as an unrestricted file upload and download issue that permits unauthenticated attackers to abuse the products' web-facing functionality, including the /Synchronization endpoint referenced by reporting, to perform arbitrary file read/write operations. Multiple sources in the provided content state that exploitation through the web interface can be used to upload malicious files or templates and execute arbitrary system commands, resulting in remote code execution. Reported in-the-wild activity included installation of malicious Freemarker template backdoor code and reverse-shell access on compromised systems.

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ANALYST BRIEF

Impact, mitigation & remediation

What it means. What to do now. Patch path, mitigations, and the assume-compromise checklist.

Impact

What an attacker gets, and what they’ve been doing with it.

Successful exploitation can result in full compromise of the affected Cleo MFT server. The provided reporting indicates attackers were able to achieve unauthenticated remote code execution, install backdoors, open reverse shells, execute arbitrary system commands, steal data, and use the compromised host as a foothold for further intrusion activity. CISA confirmed exploitation in ransomware attacks, and multiple reports tie the flaw to large-scale data-theft and extortion campaigns affecting organizations using exposed Cleo products.

Mitigation

If you can’t patch tonight, do this now.

If immediate patching is not possible, reduce exposure of the Cleo web interface and related endpoints to untrusted networks, especially internet-facing access. Monitor XML product logs and system telemetry for suspicious use of the web interface, /Synchronization activity, unexpected file uploads, autorun abuse, PowerShell or bash execution, malicious Freemarker templates, reverse shells, and Java backdoors such as Malichus. Hunt for unauthorized files written into product directories and isolate potentially compromised hosts. Because the initial patch was reported as incomplete, mitigation without full vendor updates may be insufficient.

Remediation

Patch, then assume compromise.

Upgrade Cleo Harmony, VLTrader, and LexiCom to at least version 5.8.0.21 to address CVE-2024-50623. However, the provided content also states that version 5.8.0.21 was later found to be incomplete and that Cleo subsequently released version 5.8.0.24 to address the related/newly identified CVE-2024-55956 and ongoing exploitation concerns. Based on the supplied material, the prudent remediation is to upgrade to the latest vendor-supported release, specifically no earlier than 5.8.0.24 where applicable, and follow current Cleo security guidance.
PUBLIC EXPLOITS

Exploits

4 valid exploits after Mallory filtered fakes, detection scripts, and README-only repos.

VALID 4 / 4 TOTALView more in app
CVE-2024-50623-pocMaturityPoCVerified exploit

This repository contains a proof-of-concept exploit for CVE-2024-50623. The main file, poc.py, is a Python script that takes a target host as input and sends a crafted HTTP GET request to the /Synchronization endpoint. The request includes a 'Retrieve' header with a path traversal payload (path=../../etc/passwd), attempting to read the /etc/passwd file from the target system. If the exploit is successful, the contents of the file are printed to the console. The exploit demonstrates an arbitrary file read vulnerability over the network. The repository structure is simple, consisting of a README.md with usage instructions and the poc.py exploit script.

congdong007Disclosed Apr 1, 2025pythonnetwork
Cleo-CVE-2024-50623-PoCMaturityPoCVerified exploit

This repository contains a Python exploit script (CVE-2024-50623.py) and a brief README. The script targets Cleo LexiCom servers vulnerable to CVE-2024-50623 (versions below 5.8.0.24) by interacting with the /Synchronization endpoint over HTTP or HTTPS. It first checks for the presence and version of Cleo LexiCom by parsing the Server header from a 500 response. If the target is vulnerable, the script attempts to read the Windows system.ini file using a crafted VLSync header, confirming arbitrary file read capability. It then attempts to upload a file (test.txt) and verifies the upload by reading it back. The script supports both single URL and batch mode via command-line arguments. The exploit demonstrates both file read and file upload (write) capabilities, making it operational. No hardcoded IPs or domains are present, but the /Synchronization endpoint and file paths are fingerprintable. The README provides usage instructions and a link to additional PoCs.

iSee857Disclosed Dec 31, 2024pythonnetwork
CVE-2024-50623MaturityPoCVerified exploit

This repository provides a proof-of-concept (POC) exploit for CVE-2024-50623, a critical unrestricted file upload and download vulnerability in Cleo Harmony, Cleo VLTrader, and Cleo LexiCom (versions prior to 5.8.0.21). The repository contains two files: a detailed README.md explaining the vulnerability, affected products, and usage instructions, and a Bash script (cve-2024-50623.sh) that implements the exploit logic. The exploit script allows an attacker to either read arbitrary files from the target server or upload arbitrary files to it by sending specially crafted HTTP requests to the /Synchronization endpoint. The script uses custom HTTP headers (notably 'VLSync') to instruct the server to perform file operations. The attacker can specify a proxy, the target URL, the action (read or write), the file path, and (for write) the local file to upload. The script logs actions and responses for auditing. No hardcoded IPs or domains are present, but the main fingerprintable endpoint is the '/Synchronization' path on the target server. The exploit is a POC and does not include weaponized payloads, but demonstrates the ability to read or write files, which could be leveraged for further attacks such as remote code execution. The repository is well-structured for testing and research purposes.

verylazytechDisclosed Dec 23, 2024bashnetwork
CVE-2024-50623MaturityPoCVerified exploit

This repository contains a Python proof-of-concept exploit for CVE-2024-50623, an unrestricted file upload and download vulnerability in Cleo software (likely VLTrader or Harmony). The exploit consists of a single Python script (CVE-2024-50623.py) and a README.md with usage instructions and background. The script allows an attacker to perform arbitrary file reads and writes on a vulnerable Cleo server by sending specially crafted HTTP requests to the /Synchronization endpoint, using a custom 'VLSync' header to specify the action and file path. The attacker can read any file on the server or upload arbitrary files, which could lead to further exploitation such as remote code execution if a malicious file is uploaded to an executable location. The exploit does not require authentication and targets the Cleo product on Windows platforms. The README provides clear usage examples for both file read and write operations. No detection or fake code is present; this is a functional exploit PoC.

watchtowrlabsDisclosed Dec 11, 2024pythonmarkdownnetwork
EXPOSURE SURFACE

Affected products & vendors

Products and vendors Mallory has correlated with this vulnerability. Open in Mallory to drill down to specific CPE configurations and version ranges.

VendorProductType
CleoHarmomyapplication
CleoHarmonyapplication
CleoLexicomapplication
CleoVltraderapplication

Vendor-confirmed product mapping. Mallory continuously reconciles this list against your asset inventory.

What this page doesn’t show

The version that knows your environment.

This page is what’s public. Mallory adds the parts that aren’t: which of your assets are affected, which adversaries are exploiting it right now, which detections to deploy, and what to do tonight.
Exposure mapping

Query your assets running an affected version, and investigate the blast radius.

Threat actor evidence5

Every observed campaign linking this CVE to a named adversary.

Associated malware6

Malware families riding this exploit, with evidence and IOCs.

Detection signatures2

YARA, Sigma, Snort, and vendor rules, auto-deployed to your SIEM.

Vendor-by-vendor mapping

Cross-references every affected SKU, including bundled OEM variants.

Social activity3

Community discussion across Reddit, Mastodon, and other social sources.