dbcve.org
Usg Flex 100 FirmwareOperating system · Zyxel

CVE-2023-22915

HIGH · 7.5 CVSS v3.1 Published 2023-04-24
Fix available
A fix is available. Upgrade to after 5.35 or later.
See remediation →
84/100
Remediation priority · High
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 buffer overflow vulnerability in the “fbwifi_forward.cgi” CGI program of Zyxel USG FLEX series firmware versions 4.50 through 5.35, USG FLEX 50(W) firmware versions 4.30 through 5.35, USG20(W)-VPN firmware versions 4.30 through 5.35, and VPN series firmware versions 4.30 through 5.35, which could allow a remote unauthenticated attacker to cause DoS conditions by sending a crafted HTTP request if the Facebook WiFi function were enabled 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 confidence

A buffer overflow vulnerability exists in the fbwifi_forward.cgi CGI program of Zyxel USG FLEX, USG FLEX 50(W), USG20(W)-VPN, and VPN series firewalls. A remote unauthenticated attacker can send a crafted HTTP request to trigger the overflow, causing denial of service conditions, but only if the Facebook WiFi feature is enabled on the affected device.

MitigationDisable the Facebook WiFi function on affected devices until a vendor patch is available, or apply firmware updates when released by Zyxel.

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 Flex 100 FirmwareOperating system
Affected:>= 4.50, <= 5.35
Usg Flex 100w FirmwareOperating system
Affected:>= 4.50, <= 5.35
Usg Flex 200 FirmwareOperating system
Affected:>= 4.50, <= 5.35
Usg Flex 50 FirmwareOperating system
Affected:>= 4.50, <= 5.35
Usg Flex 50w FirmwareOperating system
Affected:>= 4.30, <= 5.35
Usg Flex 500 FirmwareOperating system
Affected:>= 4.50, <= 5.35
Usg Flex 700 FirmwareOperating system
Affected:>= 4.50, <= 5.35
Vpn100 FirmwareOperating system
Affected:>= 4.50, <= 5.35

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

CVSS:3.1/AV:N/AC:L/PR:N/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 the device model
    Access the device admin interface or check the device label to confirm the exact model number. Affected models include USG Flex 100, 100w, 200, 50, 50w, 500, 700, and VPN100.
    Affected if The device model is NOT one of the listed affected models (USG Flex 100/100w/200/50/50w/500/700 or VPN100)
  2. Check the installed firmware version
    Log into the Zyxel device admin interface and navigate to the Status or System Info page to view the firmware version. Alternatively, use the CLI command 'show system-info' or 'syswrapper.sh show-status'.
    Affected if The firmware version falls OUTSIDE the range 4.30 to 5.35 (or 4.50 to 5.35 depending on model)
  3. Verify if Facebook WiFi feature is enabled
    Log into the device admin interface and navigate to the Facebook WiFi configuration page (typically under Configuration > Security > Facebook WiFi) or use the CLI command 'fbwifi get' to check the current status.
    Affected if The Facebook WiFi feature is ENABLED - this is required for the vulnerability to be exploitable

The device is vulnerable if it is an affected model (USG Flex or VPN series) with firmware between 4.30/4.50 and 5.35, AND the Facebook WiFi feature is currently 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 a release after 5.35
Interim mitigation

Disable the Facebook WiFi function on affected devices until a vendor patch is available, or apply firmware updates when released by Zyxel.

Recommended fix Moderate confidence

Firmware version > 5.35 (contact Zyxel support for exact patched release)

  1. 1. Identify the exact model number of the affected Zyxel device (USG Flex 100, 100w, 200, 50, 50w, 500, 700, or VPN100)
  2. 2. Access the Zyxel support website (www.zyxel.com) and navigate to the firmware download section for your specific model
  3. 3. Download the latest available firmware version for your device
  4. 4. Review the firmware release notes to confirm the version includes a fix for CVE-2023-22915
  5. 5. Backup the current device configuration before upgrading
  6. 6. Upload and install the new firmware through the device's web management interface or CLI
  7. 7. Verify the firmware upgrade completed successfully
  8. 8. Confirm the Facebook WiFi feature is either still needed (and now patched) or disable it if no longer required
Caveat Review release notes for any configuration or feature changes between your current version and the upgrade version

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

Fix this in Usg Flex 100 Firmware Scoped from the published advisory
  • Consultation4.0 h
  • Implementation2.0 h
  • Testing3.0 h
  • Review / QA2.0 h
11.0 hours of engineering $1,970
Get the upgrade done

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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-2023-22915 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