# CVE-2021-35036: Information disclosure in VMG3625-T50B firmware

> An authenticated attacker can read sensitive information from the configuration file due to cleartext storage in Zyxel router firmware.

- **Severity:** Medium 6.5 (`CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 1 Mar 2022
- **Updated:** 4 Aug 2024
- **Also known as:** GHSA-pp3g-h9w2-v7g4

## What is CVE-2021-35036?

CVE-2021-35036 is a medium-severity vulnerability in Zyxel VMG3625-T50B firmware, published on 1 Mar 2022. Any signed-in user can exploit it over the network, with no action from the victim.

### Official description

A cleartext storage of information vulnerability in the Zyxel VMG3625-T50B firmware version V5.50(ABTL.0)b2k could allow an authenticated attacker to obtain sensitive information from the configuration file.

Weakness: CWE-312 (Cleartext Storage of Sensitive Information)

## Which versions are affected by CVE-2021-35036?

It affects 31 products.


Products: Zyxel Ax7501-B0 Firmware, Zyxel Dx3301-T0 Firmware, Zyxel Dx5401-B0 Firmware, Zyxel Emg3525-T50b Firmware, Zyxel Emg5523-T50b Firmware, Zyxel Emg5723-T50k Firmware, Zyxel Ep240p Firmware, Zyxel Ex5401-B0 Firmware, Zyxel Ex5501-B0 Firmware, Zyxel Lte3301-Plus Firmware, Zyxel Lte5388-M804 Firmware, Zyxel Lte5388-S905 Firmware, Zyxel Lte5398-M904 Firmware, Zyxel Lte7240-M403 Firmware, Zyxel Lte7461-M602 Firmware, Zyxel Lte7480-M804 Firmware, Zyxel Lte7480-S905 Firmware, Zyxel Lte7485-S905 Firmware, Zyxel Lte7490-M804 Firmware, Zyxel Nr5101 Firmware and 11 more.

## How do I fix CVE-2021-35036?

No fix has been published for CVE-2021-35036 yet. Limit exposure of the affected software until one is available.

## Is CVE-2021-35036 being exploited?

There is no known exploitation of CVE-2021-35036 in the wild and no public exploit code.

Public exploit code:

- Zyxel super-admin credential exposure write-up across CPE/ONT/LTE/5G firmware, with an adapted VMG8825-B50B genpass lab. (github_poc): https://github.com/minanagehsalalma/zyxel-cve-2021-35036-super-admin-password-leak

## Other vulnerabilities in Zyxel VMG3625-T50B firmware

- [CVE-2025-8693](https://insights.sbomify.com/CVE-2025-8693/): Command injection in DX3300-T0 firmware (high 8.8)
- [CVE-2022-26413](https://insights.sbomify.com/CVE-2022-26413/): Command injection in VMG3312-T20A firmware (high 8.0)
- [CVE-2024-8748](https://insights.sbomify.com/CVE-2024-8748/): Memory corruption in VMG8825-T50K firmware (high 7.5)
- [CVE-2024-5412](https://insights.sbomify.com/CVE-2024-5412/): Memory corruption in VMG8825-T50K firmware (high 7.5)
- [CVE-2024-12009](https://insights.sbomify.com/CVE-2024-12009/): Command injection in EX5601-T1 firmware (high 7.2)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2021-35036 and fix it if it is affected.

What it is: CVE-2021-35036 is a medium-severity vulnerability in Zyxel VMG3625-T50B firmware, published on 1 Mar 2022. Any signed-in user can exploit it over the network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2021-35036 in the wild and no public exploit code.

Affected product: Zyxel VMG3625-T50B 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-2021-35036/ (Markdown: https://insights.sbomify.com/CVE-2021-35036/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-35036
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-35036
- OSV: https://osv.dev/vulnerability/CVE-2021-35036

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-35036/
Summaries are generated and may contain mistakes; the official description above is the record.