What’s Vulnerable › Vulnerabilities

CVE-2021-35029

• Severity: critical (CVSS 9.8 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 2.3% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2021-07-02 · updated 2026-06-17
• Weakness: CWE-287

Description

An authentication bypasss vulnerability in the web-based management interface of Zyxel USG/Zywall series firmware versions 4.35 through 4.64 and USG Flex, ATP, and VPN series firmware versions 4.35 through 5.01, which could allow a remote attacker to execute arbitrary commands on an affected device.

Affected products

• Zyxel Usg1000 Firmware: from 4.35 through 4.64
• Zyxel Usg100 Firmware: from 4.35 through 4.64
• Zyxel Usg1100 Firmware: from 4.35 through 4.64
• Zyxel Usg110 Firmware: from 4.35 through 4.64
• Zyxel Usg1900 Firmware: from 4.35 through 4.64
• Zyxel Usg20-Vpn Firmware: from 4.35 through 5.01
• Zyxel Usg2000 Firmware: from 4.35 through 4.64
• Zyxel Usg200 Firmware: from 4.35 through 4.64
• Zyxel Usg20 Firmware: from 4.35 through 4.64
• Zyxel USG20(W)-VPN firmware: from 4.35 through 5.01
• Zyxel Usg20W Firmware: from 4.35 through 4.64
• Zyxel Usg210 Firmware: from 4.35 through 4.64
• Zyxel Usg2200-Vpn Firmware: from 4.35 through 5.01
• Zyxel Usg300 Firmware: from 4.35 through 4.64
• Zyxel Usg310 Firmware: from 4.35 through 4.64
• Zyxel Usg40 Firmware: from 4.35 through 4.64
• Zyxel Usg40W Firmware: from 4.35 through 4.64
• Zyxel Usg50 Firmware: from 4.35 through 4.64
• Zyxel Usg60 Firmware: from 4.35 through 4.64
• Zyxel Usg60W Firmware: from 4.35 through 4.64
• Zyxel firewall (ZLD): from 4.35 through 5.01
• Zyxel USG FLEX 100(W) firmware: from 4.35 through 5.01
• Zyxel USG FLEX 200 firmware: from 4.35 through 5.01
• Zyxel USG FLEX 500 firmware: from 4.35 through 5.01
• Zyxel USG FLEX 700 firmware: from 4.35 through 5.01
• Zyxel Zywall 1100 Firmware: from 4.35 through 5.01
• Zyxel Zywall 110 Firmware: from 4.35 through 5.01
• Zyxel Zywall 310 Firmware: from 4.35 through 5.01
• Zyxel Zywall Atp100 Firmware: from 4.35 through 5.01
• Zyxel Zywall Atp100W Firmware: from 4.35 through 5.01

References

• https://www.zyxel.com/support/Zyxel_security_advisory_for_attacks_against_security_appliances.shtml
• https://www.zyxel.com/support/Zyxel_security_advisory_for_attacks_against_security_appliances.shtml

Get alerted when CVE-2021-35029 or the next vulnerability affects your stack