CVE-2020-25014
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 stack-based buffer overflow in fbwifi_continue.cgi on Zyxel UTM and VPN series of gateways running firmware version V4.30 through to V4.55 allows remote unauthenticated attackers to execute arbitrary code via a crafted http packet.
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 confidenceA stack-based buffer overflow vulnerability exists in the fbwifi_continue.cgi component of Zyxel UTM and VPN series gateways running firmware versions V4.30 through V4.55. Remote unauthenticated attackers can exploit this flaw via crafted HTTP packets to achieve arbitrary code execution, likely with elevated privileges on the affected device.
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>= 4.30, <= 4.55<= 6.10= 6.10all versionsCVSS 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
- High
- Integrity
- High
- Availability
- High
CVSS:3.1/AV:N/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 device modelDetermine if the target device is a Zyxel UTM or VPN series gateway by checking the device label, web interface, or SNMP inventory. Common model prefixes include USG, ZyWall, and ATP series.Affected if The device is not a Zyxel UTM or VPN gateway, then this CVE does not apply.
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Check firmware versionAccess the device web interface under Status or System Info section, or use CLI command 'show system-info' or 'sysrepoctl --version' depending on model, to retrieve the installed firmware version.Affected if The installed firmware version falls within V4.30 through V4.55 (inclusive), placing it in the affected range.
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Verify fbwifi feature statusCheck if the fbwifi or Facebook WiFi captive portal feature is enabled on the device. This is typically found under Configuration > Wireless > fbwifi or Captive Portal settings in the web GUI.Affected if The fbwifi feature is enabled, making the vulnerable fbwifi_continue.cgi component accessible.
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Confirm CGI accessibilityAttempt to access the fbwifi_continue.cgi endpoint via HTTP (for example, GET request to http://<device-ip>/fbwifi_continue.cgi) from an internal network host to verify the component responds.Affected if The CGI script responds or returns any HTTP response, confirming the component is present and reachable.
The device is affected if it is a Zyxel UTM or VPN gateway running firmware version V4.30 through V4.55 with the fbwifi feature enabled and the fbwifi_continue.cgi component accessible.
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.
From vendor dataUpgrade Zyxel UTM/VPN firmware to a version beyond V4.55 (or the latest stable release) to remediate this vulnerability; if immediate patching is not possible, consider network segmentation to limit exposure of the affected device to untrusted networks.
- Consultation4.0 h
- Implementation2.0 h
- Testing4.0 h
- Review / QA2.0 h
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Free · runs locallyCheck whether your project pulls in CVE-2020-25014 — 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-2020-25014 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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