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Vulnerability record · CVE-2021-4039 · published 1 March 2022

CVE-2021-4039: Zyxel NWA-1100-NH web interface OS command injection

Zyxel · Nwa1100 Nh Firmware

The web interface of the Zyxel NWA-1100-NH access point firmware is vulnerable to OS command injection, allowing arbitrary operating system commands to be executed on the device. The flaw is remotely reachable without authentication or user interaction, making it a serious risk for exposed access points.

9.8 CVSS 3.1 Critical EPSS 71% · top 0.6% CWE-78 · OS command injection
9.8CVSS 3.1 base score, v2 10.0
71%EPSS exploitation probability, 30 days
NoNot in CISA KEV
1Affected product versions listed by NVD
4References, 2 tagged exploit
17 Jun 2026Last modified by NVD

Description

A command injection vulnerability in the web interface of the Zyxel NWA-1100-NH firmware could allow an attacker to execute arbitrary OS commands on the device.

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Automated analysis

Generated by VULONE's analysis model from the NVD record, CISA KEV and EPSS data on 19 September 2026. Confidence: high.

critical priorityCVSS 9.8 with network reachability, no authentication, and a public exploit reference make this a high-impact, easily exploitable flaw.

What it is

The web interface of the Zyxel NWA-1100-NH access point firmware is vulnerable to OS command injection, allowing arbitrary operating system commands to be executed on the device. The flaw is remotely reachable without authentication or user interaction, making it a serious risk for exposed access points.

Impact

An attacker can execute arbitrary OS commands on the device, gaining full control over the access point, including its configuration and any data or network access it mediates.

Attack surface

Reachable over the network through the device web interface, per the CVSS vector AV:N/AC:L/PR:N/UI:N, meaning no authentication or user interaction is required.

Exploitation

Not listed in CISA KEV, but EPSS is very high (0.71, 99th percentile) and a public exploit reference exists on Packet Storm, indicating active interest and likely weaponization.

What to do

  • Apply the vendor patch from the Zyxel advisory for NWA-1100-NH firmware.
  • Restrict management web interface access to trusted internal networks and disable remote/WAN administration.
  • Segment access point management traffic from user and guest networks.
  • Monitor vendor advisories for updated firmware and replace the device if it is end-of-support.

Detection

  • Inspect web server and device logs for suspicious HTTP requests containing shell metacharacters or command strings.
  • Monitor for unexpected outbound connections or processes spawned by the web interface process.
  • Alert on configuration changes or new accounts created on the access point outside change windows.

This assessment is produced automatically and is not human-reviewed. Verify against the vendor advisory before acting on it.

Affected products

1 vulnerable configurations from NVD's CPE data, grouped by vendor and product.

References

LinkTags
http://packetstormsecurity.com/files/166752/Zyxel-NWA-1100-NH-Command-Injection.html ExploitRelease NotesThird Party AdvisoryVDB Entry
https://www.zyxel.com/support/OS-command-injection-vulnerability-of-NWA1100-NH-access-point.shtml PatchVendor Advisory
http://packetstormsecurity.com/files/166752/Zyxel-NWA-1100-NH-Command-Injection.html ExploitRelease NotesThird Party AdvisoryVDB Entry
https://www.zyxel.com/support/OS-command-injection-vulnerability-of-NWA1100-NH-access-point.shtml PatchVendor Advisory

Track CVE-2021-4039 inside VULONE

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Source: NIST National Vulnerability Database (record CVE-2021-4039), CISA KEV, FIRST EPSS (scores of 2026-09-26). This page is refreshed as NVD updates the record.