# CVE-2021-35033: Hardcoded credentials in NBG6818 series firmware

> Attackers can gain root access via physical UART connection or enabled remote assistance due to pre-configured password management flaws.

- **Severity:** High 7.8 (`CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Local or same network only
- **Victim action needed:** A user has to click or open something
- **Fix available:** No
- **Published:** 23 Nov 2021
- **Updated:** 4 Aug 2024
- **Also known as:** GHSA-pm46-rmc8-j8j3

## What is CVE-2021-35033?

CVE-2021-35033 is a high-severity vulnerability in Zyxel NBG6818 series firmware, published on 23 Nov 2021. It can only be exploited from the same machine or local network, and only if a user opens a file or follows a link.

### Official 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.

Weakness: CWE-287 (Improper Authentication), CWE-260 (Password in Configuration File)

## Which versions are affected by CVE-2021-35033?

It affects 6 products.


Products: Zyxel Nbg6818 Firmware, Zyxel Nbg7815 Firmware, Zyxel Wsq20 Firmware, Zyxel Wsq50 Firmware, Zyxel Wsq60 Firmware, Zyxel Wsr30 Firmware.

## How do I fix CVE-2021-35033?

No fix has been published for CVE-2021-35033 yet. Limit exposure of the affected software until one is available.

## Is CVE-2021-35033 being exploited?

There is no known exploitation of CVE-2021-35033 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2021-35033 and fix it if it is affected.

What it is: CVE-2021-35033 is a high-severity vulnerability in Zyxel NBG6818 series firmware, published on 23 Nov 2021. It can only be exploited from the same machine or local network, and only if a user opens a file or follows a link.
Exploitation: There is no known exploitation of CVE-2021-35033 in the wild and no public exploit code.

Affected product: Zyxel NBG6818 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-2021-35033/ (Markdown: https://insights.sbomify.com/CVE-2021-35033/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-35033
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-35033
- OSV: https://osv.dev/vulnerability/CVE-2021-35033

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-35033/
Summaries are generated and may contain mistakes; the official description above is the record.