SOURCE FACT
Zyxel · Multiple Firewalls
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.
CISA notes
https://www.zyxel.com/global/en/support/security-advisories/zyxel-security-advisory-for-remote-command-injection-vulnerability-of-firewalls; https://nvd.nist.gov/vuln/detail/CVE-2023-28771
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