dbcve.org
Usg 2200 Vpn FirmwareOperating system · Zyxel

CVE-2023-33011

HIGH · 8.8 CVSS v3.1 Published 2023-07-17
Fix available
A fix is available. Upgrade to 5.37 or later.
See remediation →
93/100
Remediation priority · Urgent
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 the Zyxel ATP series firmware versions 5.10 through 5.36 Patch 2, USG FLEX series firmware versions 5.00 through 5.36 Patch 2, USG FLEX 50(W) series firmware versions 5.10 through 5.36 Patch 2, USG20(W)-VPN series firmware versions 5.10 through 5.36 Patch 2, and VPN series firmware versions 5.00 through 5.36 Patch 2, could allow an unauthenticated, LAN-based attacker to execute some OS commands by using a crafted PPPoE configuration on an affected device when the cloud management mode is 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

A format string vulnerability in Zyxel ATP, USG FLEX, USG FLEX 50(W), USG20(W)-VPN, and VPN series firewalls allows unauthenticated LAN-based attackers to execute OS commands by sending a crafted PPPoE configuration when cloud management mode is enabled.

MitigationDisable cloud management mode if not required, or apply vendor-supplied firmware patches (beyond 5.36 Patch 2) when available to remediate the format string vulnerability in PPPoE processing.

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
Usg 2200 Vpn FirmwareOperating system
Affected:>= 5.00, < 5.37
Usg Flex 100 FirmwareOperating system
Affected:>= 5.00, < 5.37
Usg Flex 100w FirmwareOperating system
Affected:>= 5.00, < 5.37
Usg Flex 200 FirmwareOperating system
Affected:>= 5.00, < 5.37
Usg Flex 50 FirmwareOperating system
Affected:>= 5.00, < 5.37
Usg Flex 500 FirmwareOperating system
Affected:>= 5.00, < 5.37
Usg Flex 50w FirmwareOperating system
Affected:>= 5.00, < 5.37
Usg Flex 700 FirmwareOperating system
Affected:>= 5.00, < 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
Adjacent
Complexity
Low
Privileges
None
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

CVSS:3.1/AV:A/AC:L/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 the device model
    Access the firewall web interface or CLI and retrieve the model name (e.g., USG Flex 100, USG Flex 200, ATP, USG20W-VPN, USG 2200 VPN). Compare against the list of affected models in the CVE.
    Affected if The device model is one of: ATP, USG FLEX, USG FLEX 50(W), USG20(W)-VPN, or USG 2200 VPN series.
  2. Check the firmware version
    In the web interface, go to Maintenance > Firmware or use the CLI command 'show system-info' or 'sysctl | grep version' to retrieve the installed firmware version.
    Affected if The firmware version is 5.00 or higher but lower than 5.37 (or 5.36 Patch 2).
  3. Verify if cloud management mode is enabled
    In the web interface, navigate to CONFIGURATION > Cloud Management or use the CLI command 'show cloud' to check the cloud management status.
    Affected if Cloud management mode is enabled on the device.
  4. Check PPPoE configuration
    In the web interface, go to CONFIGURATION > Network > WAN or CONFIGURATION > Interface > PPPoE to see if any PPPoE connections are configured.
    Affected if PPPoE is configured and active on the device.

The device is affected if it is a matching model, runs firmware version 5.00 through 5.36 (or before Patch 2), has cloud management mode enabled, and has PPPoE configured.

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

Disable cloud management mode if not required, or apply vendor-supplied firmware patches (beyond 5.36 Patch 2) when available to remediate the format string vulnerability in PPPoE processing.

Recommended fix High confidence

Zyxel USG FLEX series firmware version 5.37 or later (or ATP/USG20-VPN/VPN series firmware version 5.37 or later depending on device model)

  1. Identify the specific USG FLEX model from the affected list (USG 2200 VPN, USG Flex 100, 100w, 200, 50, 50w, 500, or 700)
  2. Navigate to the Zyxel support website (www.zyxel.com) and locate the firmware download section for your specific device model
  3. Download firmware version 5.37 or later for your affected device
  4. Review the firmware release notes for any special upgrade instructions or prerequisites
  5. Backup the current device configuration before proceeding with the firmware update
  6. Access the device web management interface or CLI
  7. Upload and install the firmware version 5.37 or later
  8. Verify the firmware was installed successfully by checking the version in the device status
Caveat Review Zyxel release notes for version 5.37 - firmware upgrades may have configuration changes or migration requirements; test in non-production environment first

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

Fix this in Usg 2200 Vpn Firmware Scoped from the published advisory
  • Consultation2.0 h
  • Implementation1.0 h
  • Testing2.0 h
  • Review / QA1.0 h
6.0 hours of engineering $1,060
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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-2023-33011 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