CVE-2021-4029

Severity: high (CVSS 8.8 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.7% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2022-02-24 · updated 2026-06-17
Weakness: CWE-78

Description

A command injection vulnerability in the CGI program of the Zyxel ARMOR Z1/Z2 firmware could allow an attacker to execute arbitrary OS commands via a LAN interface.

Affected products

Zyxel Nbg6816 Firmware: 1.00(aawb.10)c0
Zyxel Nbg6817 Firmware: before 1.00\(abcs.11\)c0 — fixed in 1.00\(abcs.11\)c0

How to fix

Upgrade to a fixed version: Zyxel Nbg6817 Firmware 1.00\(abcs.11\)c0. Check the vendor advisory for mitigations.

References

https://www.zyxel.com/support/forgery-vulnerabilities-of-select-Armor-home-routers.shtml
https://www.zyxel.com/support/forgery-vulnerabilities-of-select-Armor-home-routers.shtml

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