CVE-2021-35033: Zyxel NBG6818 Firmware

High severity, CVSS 7.8. EPSS: 0.4% chance of exploitation in the next 30 days.

A vulnerability in specific versions of Zyxel NBG6818, NBG7815, WSQ20, WSQ50, WSQ60, and WSR30 firmware with pre-configured password management could allow an attacker to obtain root access of the device, if the local attacker dismantles the device and uses a USB-to-UART cable to connect the device, or if the remote assistance feature had been enabled by an authenticated user.

Affected products

• Zyxel NBG6818 Firmware: before 1.00\(absc.5\)c0 (fixed in 1.00\(absc.5\)c0)
• Zyxel NBG7815 Firmware: before 1.00\(absk.7\)c0 (fixed in 1.00\(absk.7\)c0)
• Zyxel WSQ20 Firmware: before 1.00\(abof.11\)c0 (fixed in 1.00\(abof.11\)c0)
• Zyxel WSQ50 Firmware: before 2.20\(abkj.7\)c0 (fixed in 2.20\(abkj.7\)c0)
• Zyxel WSQ60 Firmware: before 2.20\(abnd.8\)c0 (fixed in 2.20\(abnd.8\)c0)
• Zyxel WSR30 Firmware: before 1.00\(abmy.12\)c0 (fixed in 1.00\(abmy.12\)c0)

Published 2021-11-23. Last modified 2026-06-17.