CVE-2023-28767: Zyxel Usg 20w-VPN Firmware

High severity, CVSS 8.8. EPSS: 0.4% chance of exploitation in the next 30 days.

The configuration parser fails to sanitize user-controlled input in the Zyxel ATP series firmware versions 5.10 through 5.36, USG FLEX series firmware versions 5.00 through 5.36,  USG FLEX 50(W) series firmware versions 5.10 through 5.36, USG20(W)-VPN series firmware versions 5.10 through 5.36, and VPN series firmware versions 5.00 through 5.36. An unauthenticated, LAN-based attacker could leverage the vulnerability to inject some operating system (OS) commands into the device configuration data on an affected device when the cloud management mode is enabled.

Affected products

  • Zyxel Usg 20w-VPN Firmware: from 5.10, before 5.37 (fixed in 5.37)
  • Zyxel Usg 2200-VPN Firmware: from 5.00, before 5.37 (fixed in 5.37)
  • Zyxel Usg Flex 100 Firmware: from 5.00, before 5.37 (fixed in 5.37)
  • Zyxel Usg Flex 100w Firmware: from 5.00, before 5.37 (fixed in 5.37)
  • Zyxel Usg Flex 200 Firmware: from 5.00, before 5.37 (fixed in 5.37)
  • Zyxel Usg Flex 500 Firmware: from 5.00, before 5.37 (fixed in 5.37)
  • Zyxel Usg Flex 50 Firmware: from 5.00, before 5.37 (fixed in 5.37)
  • Zyxel Usg Flex 50w Firmware: from 5.00, before 5.37 (fixed in 5.37)
  • Zyxel Usg Flex 700 Firmware: from 5.00, before 5.37 (fixed in 5.37)
  • Zyxel Zywall ATP100 Firmware: from 5.10, before 5.37 (fixed in 5.37)
  • Zyxel Zywall ATP100W Firmware: from 5.10, before 5.37 (fixed in 5.37)
  • Zyxel Zywall ATP200 Firmware: from 5.10, before 5.37 (fixed in 5.37)
  • Zyxel Zywall ATP500 Firmware: from 5.10, before 5.37 (fixed in 5.37)
  • Zyxel Zywall ATP700 Firmware: from 5.10, before 5.37 (fixed in 5.37)
  • Zyxel Zywall ATP800 Firmware: from 5.10, before 5.37 (fixed in 5.37)
  • Zyxel Zywall VPN100 Firmware: from 5.00, before 5.37 (fixed in 5.37)
  • Zyxel Zywall VPN2S Firmware: from 5.00, before 5.37 (fixed in 5.37)
  • Zyxel Zywall VPN300 Firmware: from 5.00, before 5.37 (fixed in 5.37)
  • Zyxel Zywall VPN50 Firmware: from 5.00, before 5.37 (fixed in 5.37)
  • Zyxel Zywall VPN 100 Firmware: from 5.00, before 5.37 (fixed in 5.37)
  • Zyxel Zywall VPN 300 Firmware: from 5.00, before 5.37 (fixed in 5.37)
  • Zyxel Zywall VPN 50 Firmware: from 5.00, before 5.37 (fixed in 5.37)

Published 2023-07-17. Last modified 2026-06-17.