CVE-2024-55956 — Harmony
CRITICALCVE-2024-55956 is a critical-severity (CVSS 9.8) CWE-77 vulnerability in cleo harmony. It is in CISA's Known Exploited Vulnerabilities catalog (added 2024-12-17) and has been used in ransomware campaigns — treat it as actively exploited and patch now. A fix is available — see the affected versions and patch details below.
In Cleo Harmony before 5.8.0.24, VLTrader before 5.8.0.24, and LexiCom before 5.8.0.24, an unauthenticated user can import and execute arbitrary Bash or PowerShell commands on the host…
Exploitation Status
Actively exploited in the wild
- Confirmed by CISA's Known Exploited Vulnerabilities catalog on 2024-12-17 — including use in ransomware campaigns. Federal agencies were required to remediate by 2025-01-07.
- A successful exploit gives an attacker total control of the affected component, not partial access.
Exploitation and automatability from CISA (KEV catalog and SSVC triage) for CVE-2024-55956.
EPSS Exploitation Probability
Probability of exploitation in the next 30 days, from FIRST.org EPSS.
How urgent is this, really
CVE-2024-55956 by exploitation likelihood (EPSS) against impact (CVSS). In the shaded patch-first corner (EPSS 50%+, CVSS 7.0+).
Where this sits among everything scored
Of 394,803 CVEs with a current EPSS score, this one falls in the ≥ 90% band (highlighted). Counts from FIRST.org, log-scaled.
Description
In Cleo Harmony before 5.8.0.24, VLTrader before 5.8.0.24, and LexiCom before 5.8.0.24, an unauthenticated user can import and execute arbitrary Bash or PowerShell commands on the host system by leveraging the default settings of the Autorun directory.
Affected Products
harmonycleolexicomcleovltradercleoResearch use only. For defensive security, authorized penetration testing, and academic research only. Never execute exploit code against systems without explicit written authorization.
Detection & mitigation playbook
Vendor / applianceDetect
Inventory every cleo harmony deployment and check each version against the affected-products list above.
Fix
Apply the cleo harmony security patch or hotfix for CVE-2024-55956 on the affected version, following the vendor advisory for your exact build.
Workarounds
Stop passing untrusted input into the interpreter or shell: call the affected binary with an argument array rather than a composed command string, reject anything outside a strict allowlist of expected values, and run the component under an account that cannot reach beyond the work it legitimately does. Alongside that, restrict the management interface to trusted networks and apply the vendor's recommended configuration mitigations.
How to detect CVE-2024-55956
A community-maintained Nuclei template exists for this CVE. You can scan for it directly:
nuclei -id cve-2024-55956 -u https://target- Template
- Cleo Harmony < 5.8.0.24 - File Upload Vulnerability
- Severity
- critical
- Impact
- Unauthenticated attackers can upload and execute arbitrary Bash or PowerShell commands on the host system by exploiting the default Autorun directory settings, achieving complete system compromise.
- Remediation
- Update Cleo Harmony, VLTrader, and LexiCom to version 5.8.0.24 or later to address the arbitrary command execution vulnerability.
Template by ProjectDiscovery nuclei-templates (iamnoooob, rootxharsh, pdresearch), MIT licensed. View the full template. Scan only systems you are authorised to test.
Frequently Asked Questions
Is CVE-2024-55956 being exploited in your environment?
Detect and block the exploit chain at execution, on systems you cannot patch yet.