dbcve.org
ZldOperating system · Zyxel

CVE-2024-42059

HIGH · 7.2 CVSS v3.1 Published 2024-09-03
Fix available
A fix is available. Upgrade to 5.39 or later.
See remediation →
78/100
Remediation priority · High
Remotely reachable Zero-click

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
A post-authentication command injection vulnerability in Zyxel ATP series firmware versions from V5.00 through V5.38, USG FLEX series firmware versions from V5.00 through V5.38, USG FLEX 50(W) series firmware versions from V5.00 through V5.38, and USG20(W)-VPN series firmware versions from V5.00 through V5.38 could allow an authenticated attacker with administrator privileges to execute some OS commands on an affected device by uploading a crafted compressed language file via FTP.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · high confidence

A post-authentication command injection vulnerability exists in multiple Zyxel firewall series (ATP, USG FLEX, USG FLEX 50W, USG20W-VPN) allowing authenticated administrators to execute arbitrary OS commands by uploading a crafted compressed language file via FTP. The vulnerability stems from insufficient validation of the language file content during the FTP upload process.

MitigationUpdate firmware to a version beyond V5.38. If immediate patching is not possible, restrict FTP access to trusted management networks and limit administrator accounts to only those requiring device management capabilities.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
ZldOperating system
Affected:>= 5.00, < 5.39

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
Low
Privileges
High
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Identify Zyxel device model
    Access the device web interface or CLI and check the model name (ATP, USG FLEX, USG FLEX 50W, or USG20W-VPN)
    Affected if Device is one of the listed models and firmware version is between 5.00 and 5.38 inclusive
  2. Check firmware version
    In the web interface, go to Maintenance > Firmware or use CLI command 'show system-info' to identify the Zld firmware version
    Affected if Firmware version is >= 5.00 and < 5.39 (versions 5.00 through 5.38 are affected)
  3. Verify FTP service is enabled
    In the web interface, go to Configuration > System > FTP or use CLI to check if FTP server is active (command 'show ftp' or similar)
    Affected if FTP server is enabled and accessible, as this is the required attack vector
  4. Check administrator account access
    In the web interface, go to Configuration > Object > User/Group or CLI 'show admin-user' to list administrator accounts
    Affected if Any administrator account exists with FTP upload capability, as authentication is required for the exploit

The device is vulnerable if it is a Zyxel ATP, USG FLEX, USG FLEX 50W, or USG20W-VPN running Zld firmware version 5.00 through 5.38, has FTP service enabled, and has an administrator account that can upload language files via FTP.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Upgrade available Upgrade to 5.39 or later
Fixed in 5.39
Interim mitigation

Update firmware to a version beyond V5.38. If immediate patching is not possible, restrict FTP access to trusted management networks and limit administrator accounts to only those requiring device management capabilities.

Recommended fix High confidence

Firmware V5.39 or later for ATP, USG FLEX, USG FLEX 50(W), and USG20(W)-VPN series

  1. 1. Log into the Zyxel device web management interface as an administrator
  2. 2. Navigate to the Firmware/System section to check the current firmware version
  3. 3. Download the firmware version V5.39 or later from the official Zyxel support website (www.zyxel.com/support/download.shtml)
  4. 4. Use the device's firmware upgrade function to upload and install the new firmware file
  5. 5. After the upgrade completes, verify the device is running firmware version V5.39 or later
  6. 6. Confirm the device is functioning normally post-upgrade
Caveat Standard firmware upgrade precautions apply - ensure stable power during upgrade, backup configuration, and review release notes for any configuration changes

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in Zld Scoped from the published advisory
  • Consultation4.0 h
  • Implementation3.0 h
  • Testing4.0 h
  • Review / QA2.0 h
13.0 hours of engineering $2,300
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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2024-42059 in production — separate from our analysis above.

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
  • No weaponised exploit code, or anything meant to cause harm
  • No spam, self-promotion, credentials, or personal data