Description
A post‑authentication command injection vulnerability in the Dynamic DNS (DDNS) configuration CLI command in Zyxel ATP series firmware versions from V5.35 through V5.41, USG FLEX series firmware versions from V5.35 through V5.41, USG FLEX 50(W) series firmware versions from V5.35 through V5.41, and USG20(W)-VPN series firmware versions from V5.35 through V5.41 could allow an authenticated attacker with administrator privileges to execute operating system (OS) commands on an affected device by supplying a specially crafted string as an argument to the CLI command.
Affected products
| Vendor | Product | Affected | Fixed |
|---|---|---|---|
| Zyxel | ATP series firmware | versions from V5.35 through V5.41 | — |
| Zyxel | USG FLEX series firmware | versions from V5.35 through V5.41 | — |
| Zyxel | USG FLEX 50(W) series firmware | versions from V5.35 through V5.41 | — |
| Zyxel | USG20(W)-VPN series firmware | versions from V5.35 through V5.41 | — |
Advisories 1
- WID-SEC-2026-0316 Zyxel Firewall: Schwachstelle ermöglicht Codeausführung BSI CERT-Bund (WID) · Feb 5, 2026