CVE-2023-28767

Unauthenticated command execution via configuration parser

Published Jul 17, 2023 · Updated Nov 7, 2024

OS command injection in Zyxel firewall firmware allows remote attackers to execute operating system commands via crafted configuration data. The configuration parser fails to sanitize user-controlled input before writing it into device configuration data. Exploitation requires LAN access and cloud management mode to be enabled, and successful injection grants command execution on the appliance.

CVSS severity8.8
High
EPSS probability0.40%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

OS command injection in Zyxel firewall firmware allows remote attackers to execute operating system commands via crafted configuration data. The configuration parser fails to sanitize user-controlled input before writing it into device configuration data. Exploitation requires LAN access and cloud management mode to be enabled, and successful injection grants command execution on the appliance.

The record

CVE
CVE-2023-28767
Published
Jul 17, 2023
Updated
Nov 7, 2024
Vendor
Zyxel Networks
Product
Zyxel USG FLEX 50W Firmware
Classifications
CWE-78, T1059
Attack vector
adjacent
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jul 17, 2023CVE publishedPublication date reported by the CVE source.
  2. Nov 7, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

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

  1. Affected versionversion=5.10 <=5.36
  2. Affected versionversion=5.10 through 5.36

What conditions does exploitation require?

Attack vectoradjacent
Required privilegesunauthenticated

What is affected?

Zyxel Networks · Zyxel USG FLEX 50W Firmwareversion=5.10 <=5.36; version=5.10 through 5.36
Zyxel Networks · Zyxel ATP Series Firmwareversion=5.10 <=5.36; version=5.10 through 5.36
Zyxel Networks · Zyxel USG20(W)-VPN Series Firmwareversion=5.10 through 5.36
Zyxel Networks · Zyxel VPN Series Firmwareversion=5.00 through 5.36
Zyxel Networks · Zyxel USG FLEX Series Firmwareversion=5.0.0 <=5.36; version=5.00 through 5.36

Published CVSS scores

8.8Zyxel CorporationCVSS:3.1/AV:A/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)
Vectoradjacent
Privilegesunauthenticated
Known exploitationUnconfirmed
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.

Technologies

Your stack

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Your stack

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