# CVE-2021-35029: Auth bypass in ATP series Firmware

> Remote attackers can bypass authentication in Zyxel USG/Zywall and related series firmware to execute arbitrary commands on the device.

- **Severity:** Critical 9.8 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 2 Jul 2021
- **Updated:** 4 Aug 2024
- **Also known as:** GHSA-2h44-x2fr-537p

## What is CVE-2021-35029?

CVE-2021-35029 is a critical authentication bypass vulnerability in Zyxel ATP series Firmware, published on 2 Jul 2021. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official 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.

Weakness: CWE-287 (Improper Authentication)

## Which versions are affected by CVE-2021-35029?

It affects 37 products.


Products: Zyxel Usg1000 Firmware, Zyxel Usg100 Firmware, Zyxel Usg1100 Firmware, Zyxel Usg110 Firmware, Zyxel Usg1900 Firmware, Zyxel Usg20-Vpn Firmware, Zyxel Usg2000 Firmware, Zyxel Usg200 Firmware, Zyxel Usg20 Firmware, Zyxel Usg20w-Vpn Firmware, Zyxel Usg20w Firmware, Zyxel Usg210 Firmware, Zyxel Usg2200-Vpn Firmware, Zyxel Usg300 Firmware, Zyxel Usg310 Firmware, Zyxel Usg40 Firmware, Zyxel Usg40w Firmware, Zyxel Usg50 Firmware, Zyxel Usg60 Firmware, Zyxel Usg60w Firmware and 17 more.

## How do I fix CVE-2021-35029?

No fix has been published for CVE-2021-35029 yet. Limit exposure of the affected software until one is available.

## Is CVE-2021-35029 being exploited?

There is no known exploitation of CVE-2021-35029 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2021-35029 and fix it if it is affected.

What it is: CVE-2021-35029 is a critical authentication bypass vulnerability in Zyxel ATP series Firmware, published on 2 Jul 2021. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2021-35029 in the wild and no public exploit code.

Affected product: Zyxel ATP series Firmware. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2021-35029/ (Markdown: https://insights.sbomify.com/CVE-2021-35029/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-35029
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-35029
- OSV: https://osv.dev/vulnerability/CVE-2021-35029

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-35029/
Summaries are generated and may contain mistakes; the official description above is the record.