dbcve.org
Nas326 FirmwareOperating system · Zyxel

CVE-2023-27988

HIGH · 7.2 CVSS v3.1 Published 2023-05-30
Fix available
A fix is available. Upgrade to 5.21 or later.
See remediation →
78/100
Remediation priority · High
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
The post-authentication command injection vulnerability in the Zyxel NAS326 firmware versions prior to V5.21(AAZF.13)C0 could allow an authenticated attacker with administrator privileges to execute some operating system (OS) commands on an affected device remotely.

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\(aazf.13\)c0
Nas540 FirmwareOperating system
Affected:< 5.21\(aatb.10\)c0
Nas542 FirmwareOperating system
Affected:< 5.21\(abag.10\)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
High
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

CVSS:3.1/AV:N/AC:L/PR:H/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 5.21 or later
Fixed in 5.21
Vendor patch www.zyxel.com →
Recommended fix High confidence

Nas326: V5.21(AAZF.13)C0 | Nas540: V5.21(AATB.10)C0 | Nas542: V5.21(ABAG.10)C0

  1. Log in to the Zyxel NAS web interface with administrator credentials
  2. Navigate to Administration > Firmware/Software section or Control Panel > System > Firmware
  3. Identify the current firmware version under System Status or similar
  4. Download the appropriate firmware version from Zyxel's official support website: For Nas326 use V5.21(AAZF.13)C0, for Nas540 use V5.21(AATB.10)C0, for Nas542 use V5.21(ABAG.10)C0
  5. Upload the firmware file via the web interface or use the firmware upgrade feature
  6. Allow the device to reboot automatically - do not power off during the upgrade process
  7. After reboot, verify the new firmware version matches the target version
Caveat Firmware upgrades may cause configuration reset or service interruption; backup configuration before upgrading

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

We can perform the upgrade in your staging environment and verify nothing breaks — typical engagement from $3,200. Get the upgrade done

Scan for this in your stack

Free · runs locally
dbcve dependency scanner

Check whether your project pulls in CVE-2023-27988 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.

Get it on GitHub Scan in the browser

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-2023-27988 in production — separate from our analysis above.

No notes yet

Be the first to add a field note for this CVE — a mitigation you’ve verified, a version caveat, or a link to a working fix. Sign in above to contribute.

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