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OS Command InjectionWeakness · CWE-78

CVE-2025-11730

HIGH · 7.2 CVSS v3.1 Published 2026-02-05
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
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 the Dynamic DNS (DDNS) configuration CLI command in Zyxel ATP series firmware versions from V5.35 through V5.41, USG FLEX series firmware versions from V5.35 through V5.41, USG FLEX 50(W) series firmware versions from V5.35 through V5.41, and USG20(W)-VPN series firmware versions from V5.35 through V5.41 could allow an authenticated attacker with administrator privileges to execute operating system (OS) commands on an affected device by supplying a specially crafted string as an argument to the CLI command.

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

Post-authentication command injection vulnerability in Zyxel ATP, USG FLEX, and USG20(W)-VPN series firewall CLI. An authenticated administrator can execute arbitrary OS commands by supplying a crafted string to the Dynamic DNS (DDNS) configuration CLI command in firmware versions V5.35 through V5.41.

MitigationUpgrade firmware to V5.42 or later to patch the vulnerability; if immediate upgrade is not feasible, restrict administrative access to trusted users only and monitor for suspicious DDNS configuration activity.

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

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 the firewall model
    Access the device web GUI or CLI and retrieve the exact model name (ATP, USG FLEX, or USG20(W)-VPN series)
    Affected if Model is not one of ATP, USG FLEX, or USG20(W)-VPN series
  2. Check the installed firmware version
    Via CLI, run 'show system-info' or via web GUI navigate to Maintenance > Firmware to view the current firmware version
    Affected if Version is between V5.35 and V5.41 inclusive (V5.35, V5.36, V5.37, V5.38, V5.39, V5.40, V5.41)
  3. Verify DDNS feature availability
    In the CLI, navigate to the DDNS configuration mode (typically via 'configure terminal' then 'ddns' or check help for ddns commands)
    Affected if DDNS configuration commands are accessible and the device is running an affected firmware version
  4. Confirm administrative access exists
    Verify you have valid administrator-level credentials for the device CLI
    Affected if You can authenticate as administrator AND the device firmware is in the affected V5.35-V5.41 range AND the DDNS CLI feature is present

You are affected if your Zyxel ATP, USG FLEX, or USG20(W)-VPN firewall runs firmware V5.35 through V5.41 and you have administrator CLI access to configure DDNS settings.

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
Mitigation available No clean upgrade yet — mitigate in the meantime
Mitigation

Upgrade firmware to V5.42 or later to patch the vulnerability; if immediate upgrade is not feasible, restrict administrative access to trusted users only and monitor for suspicious DDNS configuration activity.

Recommended fix Moderate confidence

Firmware version V5.42 or later (check Zyxel support for exact fixed release for your model)

  1. 1. Identify the exact model number of the Zyxel device (ATP series, USG FLEX series, USG FLEX 50(W) series, or USG20(W)-VPN series)
  2. 2. Access the Zyxel support website at www.zyxel.com and navigate to the product's download/firmware page
  3. 3. Check for firmware versions beyond V5.41 (such as V5.42 or later) which should contain the security fix
  4. 4. Download the latest stable firmware version available for your specific model
  5. 5. Review the firmware release notes to confirm the fix for CVE-2025-11730 is included
  6. 6. Backup the current device configuration before upgrading
  7. 7. Follow Zyxel's standard firmware upgrade procedure for your device series
  8. 8. After upgrade, verify the device is functioning correctly and the DDNS feature works as expected
Caveat Review release notes for any configuration or feature changes between V5.41 and the target upgrade version

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

Have this fixed Scoped from the published advisory
  • Consultation3.0 h
  • Implementation4.0 h
  • Testing3.0 h
  • Review / QA2.0 h
12.0 hours of engineering $2,130
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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-2025-11730 in production — separate from our analysis above.

No notes yet

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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