Security readout for executives and security teams
Plain-English summary
Affected Zyxel NAS devices can be compromised before login by a crafted HTTP request that may run operating system commands. CISA lists CVE-2023-27992 as known exploited, so internet-exposed devices should be treated as urgent business risk.
Executive priority
Prioritize immediate remediation for any affected Zyxel NAS exposed to the internet or partner networks. KEV status and pre-authentication remote command execution make this a critical exposure with potential data theft, tampering, or service disruption impact.
Technical view
CVE-2023-27992 is a CWE-78 pre-authentication command injection in Zyxel NAS326, NAS540, and NAS542 firmware. It is network-reachable, low-complexity, requires no privileges or user interaction, and has CVSS 3.1 score 9.8 with high confidentiality, integrity, and availability impact.
Likely exposure
Exposure is limited to Zyxel NAS326 firmware before V5.21(AAZF.14)C0, NAS540 before V5.21(AATB.11)C0, and NAS542 before V5.21(ABAG.11)C0. Risk is highest when NAS web interfaces are reachable from untrusted networks.
Exploitation context
Active exploitation is supported by CISA KEV listing. The source bundle describes remote unauthenticated command execution through crafted HTTP requests, but does not provide campaign details, attacker tooling, or exploitation volume.
Researcher notes
The bundle supports affected models, fixed firmware thresholds, CWE-78 classification, CVSS vector, and KEV status. It does not include exploit indicators, proof-of-concept details, forensic artifacts, or compensating controls beyond vendor update direction.
Mitigation direction
- Upgrade NAS326 to V5.21(AAZF.14)C0 or later.
- Upgrade NAS540 to V5.21(AATB.11)C0 or later.
- Upgrade NAS542 to V5.21(ABAG.11)C0 or later.
- Restrict NAS web access to trusted networks until patched.
- Review Zyxel advisory for any product-specific operational guidance.
Validation and detection
- Inventory Zyxel NAS326, NAS540, and NAS542 assets.
- Confirm each device firmware version against the fixed versions.
- Check whether NAS web interfaces are internet-accessible.
- Review logs for suspicious unauthenticated HTTP activity.
- Verify patches after maintenance by rechecking firmware versions.
Public sources used
Michael Williams reviewed this cited source version on .
Conservative CVE-to-ATT&CK context
These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.
ATT&CK lookup starting points
Use these exact CWE pages and searches to review the Glexia ATT&CK library from this CVE's weakness and description context.
CWE-78: Command execution behavior lookup
Command injection weaknesses can lead defenders to review execution techniques and command interpreter telemetry. Open the exact CWE lookup page first, then review the ATT&CK searches from that MITRE weakness context. This is a Glexia lookup hint, not an official ATT&CK mapping.
Open ATT&CK lookupExecution behavior lookup
The CVE wording references code or command execution, so execution technique review may help defensive triage. This is a Glexia inferred lookup path, not an official MITRE, ATT&CK, or CVE Program mapping.
Open ATT&CK lookupCVE-2023-27992 mapping review
Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.
Open ATT&CK lookup- Severity
- Critical
- CVSS
- 9.8 (3.1)
- Known Exploited
- Yes
- Published
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
CNA and ADP enrichment extracted from CVE v5
These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.
CISA KEV status
CVSS vector scores
1 official scoreWe collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H3.95.9Primary CVE scoreVulnerability scoring details
Base CVSS 3.1 score
9.8CriticalVector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Source materials
- CVE List V5 sourceCVE List V5
- https://www.zyxel.com/global/en/support/security-advisories/zyxel-security-advisory-for-pre-authentication-command-injection-vulnerability-in-nas-productsCVE reference
- https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2023-27992CVE reference · government-resource
Products and packages named in the record
CWE details
CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.
Improper Neutralization of Special Elements used in an OS Command ('OS Command Injection')
Improper Neutralization of Special Elements used in an OS Command ('OS Command Injection') represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.