What’s Vulnerable › Vulnerabilities

CVE-2021-35033

• Severity: high (CVSS 7.8 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.4% probability of exploitation in the next 30 days
• Public exploit or detection template: yes
• Published: 2021-11-23 · updated 2026-06-17
• Weakness: CWE-260

Description

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

How to fix

Upgrade to a fixed version: Zyxel Nbg6818 Firmware 1.00\(absc.5\)c0; Zyxel Nbg7815 Firmware 1.00\(absk.7\)c0; Zyxel Wsq20 Firmware 1.00\(abof.11\)c0; Zyxel Wsq50 Firmware 2.20\(abkj.7\)c0; Zyxel Wsq60 Firmware 2.20\(abnd.8\)c0; Zyxel Wsr30 Firmware 1.00\(abmy.12\)c0. Check the vendor advisory for mitigations.

References

• https://www.tenable.com/security/research/tra-2022-06
• https://www.zyxel.com/support/Zyxel_security_advisory_for_pre-configured_password_management_vulnerability_of_home_routers_and_WiFi_systems.shtml
• https://www.tenable.com/security/research/tra-2022-06
• https://www.zyxel.com/support/Zyxel_security_advisory_for_pre-configured_password_management_vulnerability_of_home_routers_and_WiFi_systems.shtml

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