CVE-2023-28771: Zyxel Multiple Firewalls OS Command Injection Vulnerability

Vulnerability summary

CVE-2023-28771 is a critical (CVSS 9.8) OS Command Injection vulnerability in Zyxel Multiple Firewalls. It is known to be exploited: CISA and CIRCL list it, first on 31-05-2023. EPSS estimates a 99.28% chance of exploitation in the next 30 days, higher than 99.9% of scored vulnerabilities. 2 public exploits are recorded.

Timeline

1. 25-04-2023
   PublishedVulnerability first disclosed.
2. 31-05-2023
   Added to CISA KEVZyxel Multiple Firewalls OS Command Injection Vulnerability
3. 21-06-2023
   CISA remediation dueApply updates per vendor instructions.
4. 01-01-2025
   Added to CIRCL KEVAdded to the CIRCL known exploited vulnerabilities catalog.
5. 21-10-2025
   Last modifiedVulnerability information updated.

Description

Improper error message handling in Zyxel ZyWALL/USG series firmware versions 4.60 through 4.73, VPN series firmware versions 4.60 through 5.35, USG FLEX series firmware versions 4.60 through 5.35, and ATP series firmware versions 4.60 through 5.35, which could allow an unauthenticated attacker to execute some OS commands remotely by sending crafted packets to an affected device.

• CWE-78Improper Neutralization of Special Elements used in an OS Command ('OS Command Injection')The product constructs all or part of an OS command using externally-influenced input from an upstream component, but it does not neutralize or incorrectly neutralizes special elements that could modify the intended OS command when it is sent to a downstream component.