CVE-2021-4039Known exploitationPublic exploitNetwork attack vector

Unauthenticated command execution via login username

Published Mar 1, 2022 · Updated Aug 3, 2024

OS command injection in Zyxel NWA1100-NH firmware 2.12(AASI.0)C0 allows remote attackers to execute arbitrary commands via its web interface. The unauthenticated login handler passes the myname form parameter, including shell metacharacters, into an operating-system command without neutralization. Network reachability to the management web interface is sufficient; successful exploitation grants command execution on the access point.

CVSS severity9.8
Critical
EPSS probability71.05%
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 NWA1100-NH firmware 2.12(AASI.0)C0 allows remote attackers to execute arbitrary commands via its web interface. The unauthenticated login handler passes the myname form parameter, including shell metacharacters, into an operating-system command without neutralization. Network reachability to the management web interface is sufficient; successful exploitation grants command execution on the access point.

The record

CVE
CVE-2021-4039
Published
Mar 1, 2022
Updated
Aug 3, 2024
Vendor
Zyxel Networks
Product
NWA1100-NH Firmware
Classifications
CWE-78, T1190
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Mar 1, 2022CVE publishedPublication date reported by the CVE source.
  2. Aug 3, 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=2.12(AASI.0)C0

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Zyxel Networks · NWA1100-NH Firmwareversion=2.12(AASI.0)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
10.0NIST NVDAV:N/AC:L/Au:N/C:C/I:C/A:C

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

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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