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ZldOperating system · Zyxel

CVE-2023-5650

MEDIUM · 5.5 CVSS v3.1 Published 2023-11-28
Fix available
A fix is available. Upgrade to after 5.37 or later.
See remediation →
57/100
Remediation priority · Elevated
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
An improper privilege management vulnerability in the ZySH of the Zyxel ATP series firmware versions 4.32 through 5.37, USG FLEX series firmware versions 4.50 through 5.37, USG FLEX 50(W) series firmware versions 4.16 through 5.37, USG20(W)-VPN series firmware versions 4.16 through 5.37, and VPN series firmware versions 4.30 through 5.37, could allow an authenticated local attacker to modify the URL of the registration page in the web GUI of 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

This is an improper privilege management vulnerability in ZySH (Zyxel's command shell) affecting multiple Zyxel security appliance series. An authenticated local attacker with valid credentials can modify the URL of the registration page in the web GUI, potentially allowing phishing or social engineering attacks against other users of the device.

MitigationApply vendor firmware updates to all affected devices; until patched, limit local access to trusted administrators only and monitor for unauthorized changes to the registration page.

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
ZldOperating system
Affected:>= 4.32, <= 5.37>= 4.50, <= 5.37>= 4.16, <= 5.37>= 4.30, <= 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
Local
Complexity
Low
Privileges
Low
User interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
High
Availability
None

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:N

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 Zyxel device and firmware version
    Access the device's web GUI or CLI and locate the firmware version information. In the web GUI, this is typically found under Status or System Info pages. Via CLI, use commands like 'show system-info' or 'sysman reboot -v'.
    Affected if The device is a Zyxel security appliance running ZySH with firmware version 4.16 to 5.37, 4.30 to 5.37, 4.32 to 5.37, or 4.50 to 5.37 (any version <= 5.37 in these ranges).
  2. Verify current registration page URL configuration
    In the web GUI, navigate to the registration or welcome page configuration section. This is typically under Setup > Registration or a similar path depending on the appliance series. Document the current URL configured for the registration redirect.
    Affected if The registration page URL has been changed from the default to an unfamiliar or suspicious external URL.
  3. Review recent configuration changes
    Check the device's configuration history or audit logs for recent changes to registration, welcome page, or redirect settings. In CLI, use 'show configuration history' or similar logging commands if available.
    Affected if There are unauthorized or unexpected configuration changes related to registration page or URL redirection settings.
  4. Check for unexpected local administrator accounts
    Review the list of local administrator accounts on the device via the web GUI (typically under Admin Users or User Management) or CLI (commands like 'show admin-user' or 'aaa user'). Look for accounts you did not create or that belong to untrusted individuals.
    Affected if Unexpected local administrator accounts exist, indicating potential unauthorized access.

A user is affected if they are running any Zyxel security appliance with ZySH firmware version 5.37 or lower from the affected version ranges, where an attacker with local authenticated access could have modified the registration page URL.

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.

From vendor data
Upgrade available Upgrade to a release after 5.37
Interim mitigation

Apply vendor firmware updates to all affected devices; until patched, limit local access to trusted administrators only and monitor for unauthorized changes to the registration page.

Fix this in Zld Scoped from the published advisory
  • Consultation4.0 h
  • Implementation8.0 h
  • Testing4.0 h
  • Review / QA2.0 h
18.0 hours of engineering $3,200
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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-2023-5650 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