VulnTideExploited vulnerabilities, by vendor. Data as of .
Known exploitedIn CISA's KEV catalog since Ransomware use: unknown
Zyxel Multiple Network-Attached Storage (NAS) Devices

CVE-2023-27992: Zyxel Multiple NAS Devices Command Injection Vulnerability

Is it exploited?

Yes. CISA added it to the Known Exploited Vulnerabilities catalog on , 4 days after the CVE record was published.

How likely is exploitation in the next 30 days?
82.3%

EPSS score, percentile 99.7 of all scored records

How severe?
9.8 Critical

CVSS v3.1 base score, given by the CNA

What should I do?

CISA deadline . Apply updates per vendor instructions.

The CVE record links no vendor advisory, patch or mitigation.

Which versions are affected?

Affected

  • < V5.21(AAZF.14)C0
  • < V5.21(AATB.11)C0
  • < V5.21(ABAG.11)C0

Versions by product

Source: CISA Known Exploited Vulnerabilities (KEV) catalog, 2026.10.28, as of ; FIRST Exploit Prediction Scoring System (EPSS), v2026.06.15, as of ; CVE List V5 (CVE Program), cve_2026-10-28_0000Z, as of . About the data.

What to do

Required action, set by CISA

Apply updates per vendor instructions.

CISA due date for this action: .

Advisories and patches

The CVE record links no vendor advisory, patch or mitigation.

Linked from CISA's catalog entry

Affected products and versions

As listed in the CVE record.

Zyxel NAS326 firmware
StatusVersions
Affected< V5.21(AAZF.14)C0

Versions not listed are: unaffected.

Zyxel NAS540 firmware
StatusVersions
Affected< V5.21(AATB.11)C0

Versions not listed are: unaffected.

Zyxel NAS542 firmware
StatusVersions
Affected< V5.21(ABAG.11)C0

Versions not listed are: unaffected.

Source: CVE List V5 (CVE Program), cve_2026-10-28_0000Z, as of . About the data.

About this vulnerability

Multiple Zyxel network-attached storage (NAS) devices contain a pre-authentication command injection vulnerability that could allow an unauthenticated attacker to execute commands remotely via a crafted HTTP request.

Summary: CISA's KEV catalog, as of .

  • CISA added CVE-2023-27992 to its Known Exploited Vulnerabilities (KEV) catalog on 23 Jun 2023.
  • CISA's ransomware flag for this entry is "Unknown": no evidence of ransomware use in the catalog, which is not proof of none.
  • The due date CISA sets for the required action is 14 Jul 2023.
  • The CVE record was published on 19 Jun 2023, 4 days before it was added to KEV.
  • The CVE record carries a CVSS v3.1 base score of 9.8 (Critical), given by its CNA.
  • FIRST's EPSS model puts the probability of exploitation in the next 30 days at 82.3% (percentile 99.7), as of 28 Oct 2026.
  • CISA's SSVC assessment in the CVE record: exploitation active, automatable yes, technical impact total.

Source: CISA Known Exploited Vulnerabilities (KEV) catalog, 2026.10.28, as of ; CVE List V5 (CVE Program), cve_2026-10-28_0000Z, as of ; FIRST Exploit Prediction Scoring System (EPSS), v2026.06.15, as of . About the data.

Description

The pre-authentication command injection vulnerability in the Zyxel NAS326 firmware versions prior to V5.21(AAZF.14)C0, NAS540 firmware versions prior to V5.21(AATB.11)C0, and NAS542 firmware versions prior to V5.21(ABAG.11)C0 could allow an unauthenticated attacker to execute some operating system (OS) commands remotely by sending a crafted HTTP request.

Source: CVE List V5 (CVE Program), cve_2026-10-28_0000Z, as of . About the data.

Weakness

  • CWE-78: Improper Neutralization of Special Elements used in an OS Command ('OS Command Injection')

CWE and CAPEC are maintained by MITRE; the entries are those named in the CVE record and the KEV entry.

Timeline

DateEvent
CVE record published
Added to CISA KEV
CISA due date for the required action
CVE record last updated

References

More exploited Zyxel vulnerabilities

  • CVE-2026-7273: Zyxel GS1900 Series Switches Stack-Based Buffer Overflow Vulnerability (added )
  • CVE-2024-40890: Zyxel DSL CPE OS Command Injection Vulnerability (added )
  • CVE-2024-40891: Zyxel DSL CPE OS Command Injection Vulnerability (added )
  • CVE-2024-11667: Zyxel Multiple Firewalls Path Traversal Vulnerability (added )
  • CVE-2017-6884: Zyxel EMG2926 Routers Command Injection Vulnerability (added )
  • CVE-2017-18368: Zyxel P660HN-T1A Routers Command Injection Vulnerability (added )