CVE-2023-27992Known exploitationNetwork attack vector

Pre-authentication command execution via crafted HTTP requests

Published Jun 19, 2023 · Updated Oct 21, 2025

OS command injection in Zyxel NAS326, NAS540, and NAS542 firmware allows remote attackers to execute commands via crafted HTTP requests. Zyxel has not disclosed the affected HTTP endpoint, parameter, or command-construction routine, so the exact unsafe input handling remains publicly undisclosed. No authentication or user interaction is required, and successful exploitation executes operating-system commands remotely on the NAS appliance.

CVSS severity9.8
Critical
EPSS probability83.79%
Next 30 days · Sep 16, 2026
Known exploitationReported
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

OS command injection in Zyxel NAS326, NAS540, and NAS542 firmware allows remote attackers to execute commands via crafted HTTP requests. Zyxel has not disclosed the affected HTTP endpoint, parameter, or command-construction routine, so the exact unsafe input handling remains publicly undisclosed. No authentication or user interaction is required, and successful exploitation executes operating-system commands remotely on the NAS appliance.

The record

CVE
CVE-2023-27992
Published
Jun 19, 2023
Updated
Oct 21, 2025
Vendor
Zyxel Networks
Product
NAS542 Firmware
Classifications
CWE-78, T1059
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jun 19, 2023CVE publishedPublication date reported by the CVE source.
  2. Oct 21, 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=< V5.21(ABAG.11)C0

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Zyxel Networks · NAS542 Firmwareversion=< V5.21(ABAG.11)C0
Zyxel Networks · NAS326 Firmwareversion=< V5.21(AAZF.14)C0
Zyxel Networks · NAS540 Firmwareversion=< V5.21(AATB.11)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 exploitUnconfirmed

Weakness, pattern, technique

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

Public exploit references

No public exploit references are available in this record.

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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