CVE-2023-4473Known exploitationPublic exploitNetwork attack vector

Unauthenticated OS command execution via crafted URLs

Published Nov 30, 2023 · Updated Dec 16, 2025

Command injection in Zyxel NAS326 5.21(AAZF.14)C0 and NAS542 5.21(ABAG.11)C0 allows remote attackers to execute OS commands. The web server incorporates attacker-controlled data from a crafted URL into an OS command without neutralizing command syntax. No authentication or user interaction is required, and the executed commands can read or alter stored data or interrupt appliance service.

CVSS severity9.8
Critical
EPSS probability41.35%
Next 30 days · Sep 16, 2026
Known exploitationReported
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Command injection in Zyxel NAS326 5.21(AAZF.14)C0 and NAS542 5.21(ABAG.11)C0 allows remote attackers to execute OS commands. The web server incorporates attacker-controlled data from a crafted URL into an OS command without neutralizing command syntax. No authentication or user interaction is required, and the executed commands can read or alter stored data or interrupt appliance service.

The record

CVE
CVE-2023-4473
Published
Nov 30, 2023
Updated
Dec 16, 2025
Vendor
Zyxel Networks
Product
NAS542 Firmware
Classifications
CWE-78, T1190, T1059
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Nov 30, 2023CVE publishedPublication date reported by the CVE source.
  2. Dec 16, 2025Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=5.21\(abag.11\)c0
  2. Affected versionversion=V5.21(ABAG.11)C0

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Zyxel Networks · NAS542 Firmwareversion=5.21\(abag.11\)c0; version=V5.21(ABAG.11)C0
Zyxel Networks · NAS326 Firmwareversion=5.21\(aazf.14\)c0; version=V5.21(AAZF.14)C0

Published CVSS scores

9.8Zyxel CorporationCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationReported
Public exploitPublished

Weakness, pattern, technique

CWE-78Improper Neutralization of Special Elements used in an OS Command ('OS Command Injection')
T1190Exploit Public-Facing Application
T1059Command and Scripting Interpreter

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Reported exploitation

Technologies

Your stack

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Your stack

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