CVE-2023-28771

What is affected

Vendor	Zyxel
Product	Multiple Firewalls
Weakness	CWE-78

The vulnerability

Zyxel ATP, USG FLEX, VPN, and ZyWALL/USG firewalls allow for improper error message handling which could allow an unauthenticated attacker to execute OS commands remotely by sending crafted packets to an affected device.

Required action

Apply updates per vendor instructions.

US federal civilian agencies were required to act by 21 June 2023 under BOD 22-01. The deadline is a compliance date, not a measure of severity — it says nothing about how dangerous the flaw is to anyone else.

Where this comes from

Every field on this page is taken from the CISA Known Exploited Vulnerabilities catalog, last synced 12 Nov 2026, 00:29. Nothing here is our own assessment. For the technical scoring, see the NVD record below.

NVD record ↗ CVE.org record ↗