CVE-2021-35029

Name: CVE-2021-35029
Creator: NVD / NIST
Published: 2021-07-02T11:15:08.93+00:00
License: https://creativecommons.org/publicdomain/zero/1.0/

CRITICALCVSS 9.8/10EPSS 2.25%

Last modified Jun 17, 2026

CVE-2021-35029 is a critical-severity vulnerability rated 9.8/10 on the CVSS scale. 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.. EPSS estimates a 2.25% chance of exploitation in the next 30 days.

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.

Metrics

CVSS 3.1

9.8/10

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

EPSS Probability

2.25%

80.7th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

Affected Software

Vendor	Product	Versions
Zyxel	Usg1900 Firmware	>= 4.35, <= 4.64
Zyxel	Usg1100 Firmware	>= 4.35, <= 4.64
Zyxel	Usg310 Firmware	>= 4.35, <= 4.64
Zyxel	Usg210 Firmware	>= 4.35, <= 4.64
Zyxel	Usg110 Firmware	>= 4.35, <= 4.64
Zyxel	Usg40 Firmware	>= 4.35, <= 4.64
Zyxel	Usg40w Firmware	>= 4.35, <= 4.64
Zyxel	Usg60 Firmware	>= 4.35, <= 4.64
Zyxel	Usg60w Firmware	>= 4.35, <= 4.64
Zyxel	Usg300 Firmware	>= 4.35, <= 4.64
Zyxel	Usg1000 Firmware	>= 4.35, <= 4.64
Zyxel	Usg2000 Firmware	>= 4.35, <= 4.64
Zyxel	Usg20 Firmware	>= 4.35, <= 4.64
Zyxel	Usg20w Firmware	>= 4.35, <= 4.64
Zyxel	Usg50 Firmware	>= 4.35, <= 4.64
Zyxel	Usg100 Firmware	>= 4.35, <= 4.64
Zyxel	Usg200 Firmware	>= 4.35, <= 4.64
Zyxel	Usg Flex 100 Firmware	>= 4.35, <= 5.01
Zyxel	Usg Flex 200 Firmware	>= 4.35, <= 5.01
Zyxel	Usg Flex 500 Firmware	>= 4.35, <= 5.01
Zyxel	Usg Flex 100w Firmware	>= 4.35, <= 5.01
Zyxel	Usg Flex 700 Firmware	>= 4.35, <= 5.01
Zyxel	Zywall Atp100 Firmware	>= 4.35, <= 5.01
Zyxel	Zywall Atp100w Firmware	>= 4.35, <= 5.01
Zyxel	Zywall Atp200 Firmware	>= 4.35, <= 5.01
Zyxel	Zywall Atp500 Firmware	>= 4.35, <= 5.01
Zyxel	Zywall Atp700 Firmware	>= 4.35, <= 5.01
Zyxel	Zywall Atp800 Firmware	>= 4.35, <= 5.01
Zyxel	Zywall Vpn50 Firmware	>= 4.35, <= 5.01
Zyxel	Zywall Vpn100 Firmware	>= 4.35, <= 5.01
Zyxel	Zywall Vpn300 Firmware	>= 4.35, <= 5.01
Zyxel	Usg20-Vpn Firmware	>= 4.35, <= 5.01
Zyxel	Usg20w-Vpn Firmware	>= 4.35, <= 5.01
Zyxel	Usg2200-Vpn Firmware	>= 4.35, <= 5.01
Zyxel	Zywall 110 Firmware	>= 4.35, <= 5.01
Zyxel	Zywall 310 Firmware	>= 4.35, <= 5.01
Zyxel	Zywall 1100 Firmware	>= 4.35, <= 5.01

References

Timeline

Published: Jul 2, 2021
Last Modified: Jun 17, 2026
Status: Modified

Frequently Asked Questions

What is CVE-2021-35029?

How severe is CVE-2021-35029?

CVE-2021-35029 has a CVSS score of 9.8/10 (CRITICAL severity). The EPSS model estimates a 2.25% probability of exploitation in the next 30 days.

How do I fix CVE-2021-35029?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

Are you affected by CVE-2021-35029?

Run a free Strix scan to check your systems for this vulnerability.

Scan your code now

Source: NVD / NIST