CVE-2023-28771Known exploitationPublic exploitNetwork attack vector

Root command execution via IKEv2 error logging

Published Apr 25, 2023 · Updated Oct 21, 2025

OS command injection in Zyxel ATP, USG FLEX, VPN, and ZyWALL/USG firmware allows remote attackers to execute commands as root. The IKEv2 Notify decoder passes attacker-controlled notification data to an error logger that embeds it in an echo command executed by system(). Unauthenticated access to UDP port 500 on the WAN interface is sufficient; affected versions are 4.60 through 5.35, or 4.60 through 4.73 for ZyWALL/USG.

CVSS severity9.8
Critical
EPSS probability99.28%
Next 30 days · Nov 1, 2026
Known exploitationReported
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

OS command injection in Zyxel ATP, USG FLEX, VPN, and ZyWALL/USG firmware allows remote attackers to execute commands as root. The IKEv2 Notify decoder passes attacker-controlled notification data to an error logger that embeds it in an echo command executed by system(). Unauthenticated access to UDP port 500 on the WAN interface is sufficient; affected versions are 4.60 through 5.35, or 4.60 through 4.73 for ZyWALL/USG.

The record

CVE
CVE-2023-28771
Published
Apr 25, 2023
Updated
Oct 21, 2025
Vendor
Zyxel Networks
Product
Zyxel ATP Series Firmware
Classifications
CWE-78, T1190, T1059.004
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Apr 25, 2023CVE publishedPublication date reported by the CVE source.
  2. Jun 7, 2023Exploitation reportedDDoS botnets exploiting Zyxel IKE command injection
  3. 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=4.60 through 5.35

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Zyxel Networks · Zyxel ATP Series Firmwareversion=4.60 through 5.35
Zyxel Networks · Zyxel ZyWALL/USG Series Firmwareversion=4.60 through 4.73
Zyxel Networks · Zyxel VPN Series Firmwareversion=4.60 through 5.35
Zyxel Networks · Zyxel USG FLEX Series Firmwareversion=4.60 through 5.35

Published CVSS scores

9.8Zyxel NetworksCVSS: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.

Activity data is delayed. The latest report is Sep 28, 2026.

Daily unique IPsShadowserver observations through Sep 28, 2026. Gaps indicate unavailable data.
Sep 22, 2026Sep 28, 2026
View daily counts
Reporting dayUnique IPs
Sep 22, 2026Unavailable
Sep 23, 20261
Sep 24, 20261
Sep 25, 20262
Sep 26, 20261
Sep 27, 20261
Sep 28, 20261
Latest reporting daySep 28, 2026
Latest daily unique IPs1
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
T1059.004Command and Scripting Interpreter: Unix Shell

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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