CISA KEV · Known exploitedCritical

CVE-2023-27992

Zyxel Multiple Network-Attached Storage (NAS) Devices

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.

CVSS: 9.8
EPSS: 84.2%
CISA KEV: Listed
Published: 2023.06.19

PRIORITY ASSESSMENT

Immediate review

CISA has listed this vulnerability in the Known Exploited Vulnerabilities catalog.

Known exploitationConfirmed by CISA KEV

Exploit probability84.2%

Technical severityCVSS 9.8

Vulnerability overview

Affected product and versions

Product: Zyxel Multiple Network-Attached Storage (NAS) Devices
Affected versions: < V5.21(AAZF.14)C0, < V5.21(AATB.11)C0, < V5.21(ABAG.11)C0, < 5.21\(aazf.14\)c0, < 5.21\(aatb.11\)c0, < 5.21\(abag.11\)c0
Fixed versions: 5.21\(aazf.14\)c0, 5.21\(aatb.11\)c0, 5.21\(abag.11\)c0

Recommended response sequence

Confirm exposure before applying a vendor-supported change.

Full remediation guide

CISA required action

Apply updates per vendor instructions.

Due date: 2023.07.14

1
Identify
Confirm that Zyxel Multiple Network-Attached Storage (NAS) Devices and an affected version are present.
2
Prioritize
Combine exploitation signals with asset exposure and business criticality.
3
Remediate
Follow the vendor advisory or supported update path and preserve rollback options.
4
Verify
Recheck the version, service health, access paths, and relevant logs.

Technical data

CVSS vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
CWE: CWE-78
KEV added: 2023.06.23
Ransomware use: 미확인