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Atp100 FirmwareOperating system · Zyxel

CVE-2023-6764

HIGH · 8.1 CVSS v3.1 Published 2024-02-20
Fix available
A fix is available. Upgrade to 5.37 or later.
See remediation →
90/100
Remediation priority · Urgent
Remotely reachable No privileges 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 a function of the IPSec VPN feature 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, and USG20(W)-VPN series firmware versions from 4.16 through 5.37 Patch 1 could allow an attacker to achieve unauthorized remote code execution by sending a sequence of specially crafted payloads containing an invalid pointer; however, such an attack would require detailed knowledge of an affected device’s memory layout and configuration.

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 format string vulnerability exists in the IPSec VPN feature of multiple Zyxel firewall series (ATP, USG FLEX, USG FLEX 50W, USG20W-VPN). The flaw allows remote code execution via specially crafted payloads containing invalid pointers, though exploitation requires detailed knowledge of the device's memory layout.

MitigationApply vendor-supplied firmware updates beyond version 5.37 Patch 1. If immediate patching is not possible, restrict IPSec VPN access to trusted networks or disable the IPSec VPN service until patching can be completed.

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:>= 4.32, < 5.37= 5.37
Atp100w FirmwareOperating system
Affected:>= 4.32, < 5.37= 5.37
Atp200 FirmwareOperating system
Affected:>= 4.32, < 5.37= 5.37
Atp500 FirmwareOperating system
Affected:>= 4.32, < 5.37= 5.37
Atp700 FirmwareOperating system
Affected:>= 4.32, < 5.37= 5.37
Atp800 FirmwareOperating system
Affected:>= 4.32, < 5.37= 5.37
Usg Flex 100 FirmwareOperating system
Affected:>= 4.50, < 5.37= 5.37
Usg Flex 100ax FirmwareOperating system
Affected:>= 4.50, < 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
High
Privileges
None
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

CVSS:3.1/AV:N/AC:H/PR:N/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 Zyxel firewall's web UI (typically at https://<device-ip>) and navigate to Status > Device Information, or use CLI command 'show system-info' to confirm the exact model (ATP100, ATP100w, ATP200, ATP500, ATP700, ATP800, USG Flex 100, or USG Flex 100ax).
    Affected if Device is not one of these models: ATP100, ATP100w, ATP200, ATP500, ATP700, ATP800, USG Flex 100, USG Flex 100ax.
  2. Check firmware version
    In the web UI, go to Maintenance > Firmware > Firmware Upgrade, or run CLI command 'show version' to retrieve the installed firmware version.
    Affected if Firmware version is less than 5.37, or equals exactly 5.37 (versions 5.37 Patch 1 and later are not affected).
  3. Verify IPSec VPN status
    In the web UI, navigate to Configuration > VPN > IPSec VPN to check whether IPSec VPN is configured and active. In CLI, use 'show vpn ipsec' to list active IPSec tunnels.
    Affected if IPSec VPN is enabled with active tunnels - the vulnerability only triggers when IPSec VPN feature is in use.

Device is affected if it is an ATP or USG Flex model running firmware version 5.37 or earlier (below 5.37 or exactly 5.37) and has IPSec VPN enabled.

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

Apply vendor-supplied firmware updates beyond version 5.37 Patch 1. If immediate patching is not possible, restrict IPSec VPN access to trusted networks or disable the IPSec VPN service until patching can be completed.

Recommended fix High confidence

Firmware version 5.37 Patch 2 or later (for ATP and USG Flex series)

  1. 1. Identify the exact model and current firmware version of the affected Zyxel device (ATP100, ATP100w, ATP200, ATP500, ATP700, ATP800, USG Flex 100, or USG Flex 100ax)
  2. 2. Download the latest firmware version from the official Zyxel support website (www.zyxel.com) - look for firmware version 5.37 Patch 2 or later
  3. 3. Access the device's web management interface or CLI
  4. 4. Navigate to the firmware upgrade section (typically under System > Firmware or Maintenance > Firmware Upgrade)
  5. 5. Upload and apply the new firmware file
  6. 6. After reboot, verify the firmware version has been updated successfully
  7. 7. Verify that IPSec VPN functionality is operating normally
Caveat Standard firmware upgrade - review Zyxel release notes for any configuration changes between versions; ensure to back up current configuration before upgrading

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
  • Implementation2.0 h
  • Testing6.0 h
  • Review / QA2.0 h
14.0 hours of engineering $2,420
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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-2023-6764 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