dbcve.org
ZldOperating system · Zyxel

CVE-2025-8078

HIGH · 7.2 CVSS v3.1 Published 2025-10-21
Fix available
A fix is available. Upgrade to 5.41 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 V4.32 through V5.40, USG FLEX series firmware versions from V4.50 through V5.40, USG FLEX 50(W) series firmware versions from V4.16 through V5.40, and USG20(W)-VPN series firmware versions from V4.16 through V5.40 could allow an authenticated attacker with administrator privileges to execute operating system (OS) commands on the affected device by passing a crafted string as an argument to a 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

A post-authentication command injection vulnerability in Zyxel ATP, USG FLEX, USG FLEX 50(W), and USG20(W)-VPN series firewall devices allows an authenticated administrator to execute arbitrary OS commands by passing crafted strings as arguments to CLI commands. The vulnerability stems from insufficient input validation in the CLI command handler.

MitigationApply vendor-supplied firmware patches (V5.40 or later) to all affected devices. Until patched, strictly limit administrative access to trusted personnel only and monitor for unusual CLI command activity.

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:>= 4.32, < 5.41>= 4.50, < 5.41>= 4.16, < 5.41

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 device model
    Access the firewall web UI or CLI and determine the exact model number (ATP, USG FLEX, USG FLEX 50(W), or USG20(W)-VPN series)
    Affected if Model is NOT one of these four series - if different model, not affected by this CVE
  2. Check firmware version via CLI
    Log into the CLI and run 'show system-info' or 'show version' to display the installed firmware version
    Affected if Firmware version is installed and is lower than 5.40 (since versions below 5.41 are affected)
  3. Verify firmware version range
    Compare the installed version against the affected ranges: >= 4.16 and < 5.41 (the multiple ranges given all fall within 4.16 to 5.40 inclusive)
    Affected if Installed version falls between 4.16 and 5.40 (inclusive of 5.40, exclusive of 5.41) - if version is 5.41 or later, or below 4.16, not affected
  4. Confirm administrative access method
    Determine if the device has CLI access enabled for administrator accounts (the vulnerability requires an authenticated administrator session)
    Affected if CLI is accessible with admin credentials - however, this is a post-authentication flaw, so having CLI access alone does not guarantee exploitability, it requires a compromised or malicious admin account

The device is affected if it is an ATP, USG FLEX, USG FLEX 50(W), or USG20(W)-VPN model running firmware version 4.16 or higher but below 5.41, and an administrator can access the CLI.

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 5.41 or later
Fixed in 5.41
Interim mitigation

Apply vendor-supplied firmware patches (V5.40 or later) to all affected devices. Until patched, strictly limit administrative access to trusted personnel only and monitor for unusual CLI command activity.

Recommended fix High confidence

Upgrade to firmware version V5.41 or later for all affected series (ATP, USG FLEX, USG FLEX 50(W), USG20(W)-VPN).

  1. 1. Identify the specific Zyxel model (e.g., USG FLEX 50, ATP series) affected.
  2. 2. Log in to the Zyxel support website and navigate to the firmware download section for that specific model.
  3. 3. Download the latest firmware version. Based on the version constraints provided (< 5.41), target version **V5.41** or the latest available V5.x release.
  4. 4. Backup the current device configuration from the web interface or CLI.
  5. 5. Upload the new firmware file to the device via the 'Maintenance' > 'Firmware Upgrade' section.
  6. 6. Restart the device to complete the installation.
  7. 7. Verify the upgrade by checking the firmware version in the device status and ensure all security policies are active.
Caveat Standard upgrade procedure; device will reboot. Ensure configuration backup is saved before proceeding.

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

Fix this in Zld Scoped from the published advisory
  • Consultation3.0 h
  • Implementation6.0 h
  • Testing3.0 h
  • Review / QA2.0 h
14.0 hours of engineering $2,490
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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-2025-8078 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