CVE-2023-34139
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 · uneditedA command injection vulnerability in the Free Time WiFi hotspot feature of the Zyxel USG FLEX series firmware versions 4.50 through 5.36 Patch 2 and VPN series firmware versions 4.20 through 5.36 Patch 2, could allow an unauthenticated, LAN-based attacker to execute some OS commands on an affected device.
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 confidenceCommand injection vulnerability in the Free Time WiFi hotspot feature of Zyxel USG FLEX and VPN series firewalls. An unauthenticated attacker on the LAN can execute arbitrary OS commands due to insufficient input sanitization in the hotspot feature.
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>= 4.20, < 5.37>= 4.50, < 5.37>= 4.50, < 5.37>= 4.50, < 5.37>= 4.50, < 5.37>= 4.50, < 5.37>= 4.50, < 5.37>= 4.50, < 5.37CVSS 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 checksWork through these to decide whether this CVE applies to you.
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Identify the device modelAccess the web GUI (System > Status) or run 'show system-info' via CLI to confirm the exact model (USG 2200 VPN, USG Flex 100, 100w, 200, 50, 50w, 500, or 700)Affected if Model is NOT one of these eight affected models
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Check the firmware versionIn web GUI go to Maintenance > Firmware or run 'show system-info' via CLI to view the running firmware versionAffected if Version is >= 4.20 (for USG 2200 VPN) or >= 4.50 (for USG Flex models) AND version is < 5.37
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Verify if Free Time WiFi hotspot is enabledIn web GUI navigate to Configuration > Hotspot > Free Time or check the hotspot service status via CLI (show hotspot or related command)Affected if Free Time WiFi hotspot feature is currently enabled and configured on the device
The device is affected if it is a USG 2200 VPN, USG Flex 100/100w/200/50/50w/500/700 model running firmware version 4.20+ (or 4.50+) but below 5.37 AND the Free Time WiFi hotspot feature is enabled.
Generated from the published advisory. Verify against your own configuration.
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 · scoped5.37
Apply the latest Zyxel firmware patch beyond version 5.36 Patch 2. Until patched, restrict LAN access to untrusted users and segment guest WiFi networks from management interfaces.
Firmware version 5.37
- Identify the specific model number of the Zyxel USG FLEX or USG VPN device
- Backup the current device configuration through the web interface or CLI
- Navigate to Zyxel's official support website (www.zyxel.com) and locate the firmware download section
- Download firmware version 5.37 for the specific device model
- Access the device's web management interface and navigate to Maintenance > Firmware Upgrade
- Upload the downloaded firmware file (5.37) and initiate the upgrade process
- Wait for the device to reboot and apply the firmware (this may take several minutes)
- Verify the firmware version has been updated to 5.37 in the device status
Generated from the published advisory — verify against the referenced sources before acting.
- Consultation3.0 h
- Implementation2.0 h
- Testing3.0 h
- Review / QA1.0 h
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Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2023-34139 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.
References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesPractitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2023-34139 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
No notes yet
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- 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
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