CVE-2023-27988Public exploitNetwork attack vector

Root command execution via NTP server address

Published May 30, 2023 · Updated Jan 14, 2025

Command injection in Zyxel NAS326 Firmware V5.21(AAZF.12)C0 and earlier allows remote authenticated users to execute OS commands. The ntpdate_agent process inserts the administrator-controlled Time server address into a shell command, filtering spaces but not shell metacharacters. Administrator access to the web management interface is required, and injected commands run with root privileges, enabling device takeover or disruption.

CVSS severity7.2
High
EPSS probability1.42%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Command injection in Zyxel NAS326 Firmware V5.21(AAZF.12)C0 and earlier allows remote authenticated users to execute OS commands. The ntpdate_agent process inserts the administrator-controlled Time server address into a shell command, filtering spaces but not shell metacharacters. Administrator access to the web management interface is required, and injected commands run with root privileges, enabling device takeover or disruption.

The record

CVE
CVE-2023-27988
Published
May 30, 2023
Updated
Jan 14, 2025
Vendor
Zyxel Networks
Product
NAS326 Firmware
Classifications
CWE-78, T1059.004
Attack vector
network
Privileges
admin

Timeline

How it unfolded

  1. May 30, 2023CVE publishedPublication date reported by the CVE source.
  2. Jan 14, 2025Record 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=< V5.21(AAZF.13)C0

What conditions does exploitation require?

Attack vectornetwork
Required privilegesadmin

What is affected?

Zyxel Networks · NAS326 Firmwareversion=< V5.21(AAZF.13)C0

Published CVSS scores

7.2Zyxel CorporationCVSS:3.1/AV:N/AC:L/PR:H/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
Privilegesadmin
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-78Improper Neutralization of Special Elements used in an OS Command ('OS Command Injection')
T1059.004Unix Shell

Public exploit references

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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