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Nas326 FirmwareOperating system · Zyxel

CVE-2023-37928

HIGH · 8.8 CVSS v3.1 Published 2023-11-30
Fix available
A fix is available. Upgrade to after 5.21 or later.
See remediation →
94/100
Remediation priority · Urgent
High EPSS Remotely reachable Zero-click Patch available

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 post-authentication command injection vulnerability in the WSGI server of the Zyxel NAS326 firmware version V5.21(AAZF.14)C0 and NAS542 firmware version V5.21(ABAG.11)C0 could allow an authenticated attacker to execute some operating system (OS) commands by sending a crafted URL to a vulnerable 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
How this class of weakness works · CWE-78

User input reaches a shell or system command without being fully separated from the command itself, so an attacker can append their own instructions. Because these run with the application's privileges, it often means full control of the host. The lasting fix is to avoid the shell entirely — call APIs directly and pass arguments as data, never as concatenated strings.

General guidance for the os command injection class — the official description and references above are authoritative for this specific CVE. Want a bespoke review and a reviewed fix? Ask our team →

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
Nas326 FirmwareOperating system
Affected:<= 5.21\(aazf.14\)c0
Nas542 FirmwareOperating system
Affected:<= 5.21\(abag.11\)c0

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

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

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 5.21
Vendor patch www.zyxel.com →
Recommended fix Moderate confidence

Firmware version newer than V5.21(AAZF.14)C0 for NAS326; Firmware version newer than V5.21(ABAG.11)C0 for NAS542 - obtain exact version from Zyxel advisory

  1. 1. Visit the official Zyxel support portal at https://www.zyxel.com/global/en/support/security-advisories/zyxel-security-advisory-for-authentication-bypass-and-command-injection-vulnerabilities-in-nas-products to obtain the specific fixed firmware version for your device.
  2. 2. Identify your exact NAS model (NAS326 or NAS542).
  3. 3. Download the firmware version newer than V5.21(AAZF.14)C0 for NAS326 or newer than V5.21(ABAG.11)C0 for NAS542 from Zyxel's support site.
  4. 4. Access the web administration interface of your NAS device.
  5. 5. Navigate to Administration > Firmware Upgrade section.
  6. 6. Upload and apply the updated firmware file.
  7. 7. Verify the firmware upgrade was successful by checking the firmware version in the system information page.
  8. 8. After upgrade, confirm the device is functioning normally and all services are operational.
Caveat Review Zyxel release notes for any configuration or feature changes between versions; backup configuration before upgrading

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

We can identify the exact fixed release, upgrade, and verify it in staging — typical engagement from $3,200. 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-2023-37928 in production — separate from our analysis above.

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  • Version or environment caveats, and links to real fixes
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