What’s Vulnerable › Vulnerabilities

CVE-2023-34139

• Severity: high (CVSS 8.8 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.8% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2023-07-17 · updated 2026-06-17
• Weakness: CWE-78

Description

A command injection vulnerability in the Free Time WiFi hotspot feature of the Zyxel USG FLEX series firmware versions 4.50 through 5.36 Patch 2 and VPN series firmware versions 4.20 through 5.36 Patch 2, could allow an unauthenticated, LAN-based attacker to execute some OS commands on an affected device.

Affected products

• Zyxel Usg 2200-Vpn Firmware: from 4.20 before 5.37 — fixed in 5.37
• Zyxel firewall (ZLD): from 4.50 before 5.37 — fixed in 5.37
• Zyxel USG FLEX 100(W) firmware: from 4.50 before 5.37 — fixed in 5.37
• Zyxel USG FLEX 200 firmware: from 4.50 before 5.37 — fixed in 5.37
• Zyxel USG FLEX 500 firmware: from 4.50 before 5.37 — fixed in 5.37
• Zyxel Usg Flex 50 Firmware: from 4.50 before 5.37 — fixed in 5.37
• Zyxel USG FLEX 50(W) firmware: from 4.50 before 5.37 — fixed in 5.37
• Zyxel USG FLEX 700 firmware: from 4.50 before 5.37 — fixed in 5.37
• Zyxel Zywall Vpn100 Firmware: from 4.20 before 5.37 — fixed in 5.37
• Zyxel ZyWALL VPN2S Firmware: from 4.20 before 5.37 — fixed in 5.37
• Zyxel Zywall Vpn300 Firmware: from 4.20 before 5.37 — fixed in 5.37
• Zyxel Zywall Vpn50 Firmware: from 4.20 before 5.37 — fixed in 5.37
• Zyxel Zywall Vpn 100 Firmware: from 4.20 before 5.37 — fixed in 5.37
• Zyxel Zywall Vpn 300 Firmware: from 4.20 before 5.37 — fixed in 5.37
• Zyxel Zywall Vpn 50 Firmware: from 4.20 before 5.37 — fixed in 5.37

How to fix

Upgrade to a fixed version: Zyxel Usg 2200-Vpn Firmware 5.37; Zyxel firewall (ZLD) 5.37; Zyxel USG FLEX 100(W) firmware 5.37; Zyxel USG FLEX 200 firmware 5.37; Zyxel USG FLEX 500 firmware 5.37; Zyxel Usg Flex 50 Firmware 5.37; Zyxel USG FLEX 50(W) firmware 5.37; Zyxel USG FLEX 700 firmware 5.37; Zyxel Zywall Vpn100 Firmware 5.37; Zyxel ZyWALL VPN2S Firmware 5.37; Zyxel Zywall Vpn300 Firmware 5.37; Zyxel Zywall Vpn50 Firmware 5.37. Check the vendor advisory for mitigations.

References

• https://www.zyxel.com/global/en/support/security-advisories/zyxel-security-advisory-for-multiple-vulnerabilities-in-firewalls-and-wlan-controllers
• https://www.zyxel.com/global/en/support/security-advisories/zyxel-security-advisory-for-multiple-vulnerabilities-in-firewalls-and-wlan-controllers

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