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Cleo Multiple Products Unauthenticated File Upload Vulnerability

Exploited · KEV 2024-12-17RansomwareMetasploit moduleCVE-2024-55956CWE-276

Exploited since 2024-12-17. 2 of 8 rule sources name it; Cloudflare blocks by default. Our CRS test: blocked.

Edge rules
2/8
Our test
Blocked
CVSS
9.8
EPSS
94.0% Top 0.2%
Posts, 14d
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Published
2024-12-13

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.

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Ask about CVE-2024-55956: who's covered, what to patch first, how vendors compare. I cite sources and won't help with attacks.

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Severity, decoded

CVSS 3.1
Critical · 9.8 / 10

Exploitable over the network, with no privileges and no user interaction, leading to full loss of confidentiality, integrity and availability.

Over the internetNo login neededNo user actionWorks reliablyFull compromise
How the score is built8 metrics
  • Attack vectorAn attacker can reach it over the internet; no access to your network needed.
    Network
  • Attack complexityNo special conditions are needed; the attack works reliably.
    Low
  • Privileges requiredNo account or login is needed.
    None
  • User interactionNo one has to click or open anything; the attack works on its own.
    None
  • ScopeThe damage stays within the vulnerable component.
    Unchanged
  • Confidentiality impactAn attacker can read all data the affected component holds, or the most sensitive parts of it.
    High
  • Integrity impactAn attacker can change any data or files the affected component protects.
    High
  • Availability impactAn attacker can take the component down completely or keep it from serving anyone.
    High
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
CISA's assessmentSSVC, from the CVE record
ExploitationActive

Attackers are exploiting this in the wild.

AutomatableNo

At least one step needs hands-on work, which slows mass attacks.

Technical impactTotal

A successful attack gives full control over the affected software or all of its data.

Public exploits

2 found
1 Metasploit0 Exploit-DB1 Scanner template0 GitHub PoCs

Links are to third-party code: never run it outside an isolated lab.

Timeline

  1. 2024-12-09
    Metasploit module published
    Cleo LexiCom, VLTrader, and Harmony Unauthenticated Remote Code Execution
  2. 2024-12-13
    CVE published
    CVE List
  3. 2024-12-17
    Added to CISA KEV
    Confirmed exploitation in the wild
  4. 2025-01-13
    Cloudflare ships a rule
    Cleo Harmony - Auth Bypass - CVE:CVE-2024-55956, CVE:CVE-2024-55953
  5. 2025-01-21
    F5 ships a rule
    Cleo MFT Arbitrary File Upload
  6. 2026-11-02
    Our test: OWASP Core Rule Set blocked it
    paranoia level 1, anomaly threshold 5, default CRS settings
  7. 2026-11-02
    Our test: OWASP Core Rule Set blocked it
    paranoia level 2, anomaly threshold 5, default CRS settings

Social

2026-10-20: 0 posts2026-10-21: 0 posts2026-10-22: 0 posts2026-10-23: 0 posts2026-10-24: 0 posts2026-10-25: 0 posts2026-10-26: 0 posts2026-10-27: 0 posts2026-10-28: 0 posts2026-10-29: 0 posts2026-10-30: 0 posts2026-10-31: 0 posts2026-11-01: 0 posts2026-11-02: 0 posts

No posts seen yet on X, Bluesky, Mastodon, Hacker News or GitHub.

Vendor statements

Quoted
CloudflareWAF Managed Rules1 quoteBlocks by default

First rule 2025-01-13, 31 days after the CVE was published.

2025-01-13New rule…f49e5840Default: BlockSource
Cleo Harmony - Auth Bypass - CVE:CVE-2024-55956, CVE:CVE-2024-55953. Previous action: Log. New action: Block. New Detection
AWSAWS WAF Managed RulesNo public claim

We found no public statement from this vendor naming this CVE. That is not proof of no protection: generic rules may still catch it. AWS often describes a vulnerability without naming its CVE (for example "Log4j"). We count only entries that name the CVE, so AWS coverage is understated.

Microsoft AzureFront Door and Application Gateway WAF (DRS)No public claim

We found no public statement from this vendor naming this CVE. That is not proof of no protection: generic rules may still catch it. The rule tables name CVEs but carry no dates, so Azure is left out of every time-to-rule figure.

Google CloudCloud Armor preconfigured WAF rulesNo public claim

We found no public statement from this vendor naming this CVE. That is not proof of no protection: generic rules may still catch it. Google names few CVEs: the release notes start in May 2024 and the rules reference lists CVEs without dates. Its cve-canary rules are opt-in.

FastlyNext-Gen WAF virtual patchesBefore feed history

The CVE predates the oldest entry in this vendor's public feed, so a rule may exist that we cannot see.

F5Attack signatures (Distributed Cloud WAF)1 quoteRule published

First rule 2025-01-21, 39 days after the CVE was published.

2025-01-21New rule200104999Source
Added: signature 200104999 "Cleo MFT Arbitrary File Upload" (Server Side Code Injection, risk High), systems: Java Servlets/JSP, Other Web Server. References: CVE-2024-55956.
AkamaiApp & API Protector (Adaptive Security Engine)No public source

This vendor publishes no machine-readable rule changelog we can check.

OWASP CRSCore Rule Set (open source, used inside many WAFs)No public claim

We found no public statement from this vendor naming this CVE. That is not proof of no protection: generic rules may still catch it. CRS rarely names CVEs: it relies on generic detections. Our own lab measures what it actually blocks.