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Atp100 FirmwareOperating system · Zyxel

CVE-2023-6399

MEDIUM · 6.5 CVSS v3.1 Published 2024-02-20
Fix available
A fix is available. Upgrade to 5.37 or later.
See remediation →
71/100
Remediation priority · Elevated
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 format string vulnerability in Zyxel ATP series firmware versions from 4.32 through 5.37 Patch 1, USG FLEX series firmware versions from 4.50 through 5.37 Patch 1, USG FLEX 50(W) series firmware versions from 4.16 through 5.37 Patch 1, USG20(W)-VPN series firmware versions from 4.16 through 5.37 Patch 1, and USG FLEX H series firmware versions from 1.10 through 1.10 Patch 1 could allow an authenticated IPSec VPN user to cause DoS conditions against the “deviceid” daemon by sending a crafted hostname to an affected device if it has the “Device Insight” feature enabled.

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

Format string vulnerability in Zyxel deviceid daemon allows authenticated IPSec VPN users to send a crafted hostname (via Device Insight feature) that triggers the vulnerability, causing denial of service conditions against the deviceid daemon.

MitigationUpgrade to patched firmware versions when available; as a workaround, disable the Device Insight feature if not required; restrict IPSec VPN access to trusted users only.

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
Atp100 FirmwareOperating system
Affected:>= 5.10, < 5.37= 5.37
Atp100w FirmwareOperating system
Affected:>= 5.10, < 5.37= 5.37
Atp200 FirmwareOperating system
Affected:>= 5.10, < 5.37= 5.37
Atp500 FirmwareOperating system
Affected:>= 5.10, < 5.37= 5.37
Atp700 FirmwareOperating system
Affected:>= 5.10, < 5.37= 5.37
Atp800 FirmwareOperating system
Affected:>= 5.10, < 5.37= 5.37
Usg Flex 100 FirmwareOperating system
Affected:>= 5.10, < 5.37= 5.37
Usg Flex 100ax FirmwareOperating system
Affected:>= 5.10, < 5.37= 5.37

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
Low
User interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/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 your Zyxel device model
    Access the device web UI or CLI and note the exact model name (Atp100, Atp100w, Atp200, Atp500, Atp700, Atp800, Usg Flex 100, or Usg Flex 100ax)
    Affected if Device model matches one of these eight models
  2. Check the installed firmware version
    In the web UI, go to Maintenance > Firmware or use CLI command 'show system-info' to retrieve the firmware version
    Affected if Firmware version is greater than or equal to 5.10 and less than or equal to 5.37
  3. Verify if Device Insight feature is enabled
    In the web UI, navigate to Device Insight settings (or Security > Device Insight) and check if the feature is turned on; alternatively check via CLI
    Affected if Device Insight feature is enabled on the device
  4. Confirm IPSec VPN is configured
    In the web UI, check VPN > IPSec or use CLI command 'show vpn ipsec' to see if any IPSec VPN connections are defined
    Affected if IPSec VPN is configured and active on the device

If your device is one of the eight affected models, runs firmware version 5.10 through 5.37, has Device Insight enabled, and has IPSec VPN configured, then your environment is vulnerable to CVE-2023-6399.

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 5.37 or later
Fixed in 5.37
Interim mitigation

Upgrade to patched firmware versions when available; as a workaround, disable the Device Insight feature if not required; restrict IPSec VPN access to trusted users only.

Recommended fix High confidence

Firmware 5.37 Patch 2 or later (e.g., 5.38/5.40/5.50 depending on model availability)

  1. 1. Identify the specific model (e.g., ATP100, USG Flex 100, etc.) from the affected product list
  2. 2. Access the Zyxel support website (www.zyxel.com) and navigate to the firmware download section for your device model
  3. 3. Download firmware version 5.37 Patch 2 or later (the first version that includes the security fix)
  4. 4. Back up the current device configuration before upgrading
  5. 5. Upload and apply the new firmware through the device's web management interface or CLI
  6. 6. After reboot, verify the device is running the patched firmware version
  7. 7. Confirm the Device Insight feature is still functioning properly
Caveat Standard firmware upgrade risks apply - ensure configuration backup and planned maintenance window; some legacy IPSec VPN configurations may need review after upgrade

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

Fix this in Atp100 Firmware Scoped from the published advisory
  • Consultation4.0 h
  • Testing8.0 h
  • Review / QA2.0 h
14.0 hours of engineering $2,360
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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-2023-6399 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