# CVE-2023-35136: Information disclosure in ATP series firmware

> An authenticated local attacker can access configuration files on Zyxel ATP, USG FLEX, and VPN series devices due to improper input validation in the Quagga package.

- **Severity:** Medium 5.5 (`CVSS:3.1/AV:L/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:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 28 Nov 2023
- **Updated:** 5 Jun 2025
- **Also known as:** GHSA-7pcw-5pmh-x8wr

## What is CVE-2023-35136?

CVE-2023-35136 is a medium-severity vulnerability in Zyxel ATP series firmware, published on 28 Nov 2023. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

An improper input validation vulnerability in the “Quagga” package of the Zyxel ATP series firmware versions 4.32 through 5.37, USG FLEX series firmware versions 4.50 through 5.37, USG FLEX 50(W) series firmware versions 4.16 through 5.37, USG20(W)-VPN series firmware versions 4.16 through 5.37, and VPN series firmware versions 4.30 through 5.37, could allow an authenticated local attacker to access configuration files on an affected device.

Weakness: CWE-20 (Improper Input Validation)

## Which versions are affected by CVE-2023-35136?

It affects 1 product.


Products: Zyxel Zld.

## How do I fix CVE-2023-35136?

No fix has been published for CVE-2023-35136 yet. Limit exposure of the affected software until one is available.

## Is CVE-2023-35136 being exploited?

There is no known exploitation of CVE-2023-35136 in the wild and no public exploit code.

## Other vulnerabilities in Zyxel ATP series firmware

- [CVE-2024-11667](https://insights.sbomify.com/CVE-2024-11667/): Zyxel Multiple Firewalls Path Traversal (high 7.5, exploited in the wild)
- [CVE-2025-9133](https://insights.sbomify.com/CVE-2025-9133/): Missing authorization in ATP series firmware (high 8.1)
- [CVE-2024-42057](https://insights.sbomify.com/CVE-2024-42057/): Command injection in ATP series firmware (high 8.1)
- [CVE-2024-42058](https://insights.sbomify.com/CVE-2024-42058/): Null dereference in ATP series firmware (high 7.5)
- [CVE-2023-4398](https://insights.sbomify.com/CVE-2023-4398/): Integer overflow in ATP series firmware (high 7.5)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2023-35136 and fix it if it is affected.

What it is: CVE-2023-35136 is a medium-severity vulnerability in Zyxel ATP series firmware, published on 28 Nov 2023. It can only be exploited from the same machine or local network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2023-35136 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-2023-35136/ (Markdown: https://insights.sbomify.com/CVE-2023-35136/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2023-35136
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2023-35136
- OSV: https://osv.dev/vulnerability/CVE-2023-35136

---
From sbomify Insights: https://insights.sbomify.com/CVE-2023-35136/
Summaries are generated and may contain mistakes; the official description above is the record.