# CVE-2023-33010: Zyxel Multiple Firewalls Buffer Overflow

> Unauthenticated attackers can trigger a buffer overflow in Zyxel firewall firmware, leading to remote code execution or denial of service.

- **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:** Yes, since 5 Jun 2023 (CISA KEV)
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 24 May 2023
- **Updated:** 21 Oct 2025
- **Also known as:** GHSA-fqv9-84fh-jjgr

## What is CVE-2023-33010?

CVE-2023-33010 is a critical memory corruption vulnerability in Zyxel ATP series firmware, published on 24 May 2023. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

A buffer overflow vulnerability in the ID processing function in Zyxel ATP series firmware versions 4.32 through 5.36 Patch 1, USG FLEX series firmware versions 4.50 through 5.36 Patch 1, USG FLEX 50(W) firmware versions 4.25 through 5.36 Patch 1, USG20(W)-VPN firmware versions 4.25 through 5.36 Patch 1, VPN series firmware versions 4.30 through 5.36 Patch 1, ZyWALL/USG series firmware versions 4.25 through 4.73 Patch 1, could allow an unauthenticated attacker to cause denial-of-service (DoS) conditions and even a remote code execution on an affected device.

Weakness: CWE-120 (Buffer Copy without Checking Size of Input)

## Which versions are affected by CVE-2023-33010?

It affects 23 products.


Products: Zyxel Atp100 Firmware, Zyxel Atp100w Firmware, Zyxel Atp200 Firmware, Zyxel Atp500 Firmware, Zyxel Atp700 Firmware, Zyxel Atp800 Firmware, Zyxel Usg20-Vpn Firmware, Zyxel Usg 20w-Vpn Firmware, Zyxel Usg 40 Firmware, Zyxel Usg 40w Firmware, Zyxel Usg 60 Firmware, Zyxel Usg 60w Firmware, Zyxel Usg Flex 100 Firmware, Zyxel Usg Flex 100w Firmware, Zyxel Usg Flex 200 Firmware, Zyxel Usg Flex 500 Firmware, Zyxel Usg Flex 50 Firmware, Zyxel Usg Flex 50w Firmware, Zyxel Usg Flex 700 Firmware, Zyxel Vpn1000 Firmware and 3 more.

## How do I fix CVE-2023-33010?

No fix has been published for CVE-2023-33010 yet. Limit exposure of the affected software until one is available. US federal agencies must fix it by 26 Jun 2023.

## Is CVE-2023-33010 being exploited?

Yes. Attackers have exploited CVE-2023-33010 in the wild since at least 5 Jun 2023.

## Other vulnerabilities in Zyxel ATP series firmware

- [CVE-2023-33009](https://insights.sbomify.com/CVE-2023-33009/): Zyxel Multiple Firewalls Buffer Overflow (critical 9.8, exploited in the wild)
- [CVE-2023-28771](https://insights.sbomify.com/CVE-2023-28771/): Zyxel Multiple Firewalls OS Command Injection (critical 9.8, exploited in the wild)
- [CVE-2022-30525](https://insights.sbomify.com/CVE-2022-30525/): Zyxel Multiple Firewalls OS Command Injection (critical 9.8, exploited in the wild)
- [CVE-2020-29583](https://insights.sbomify.com/CVE-2020-29583/): Zyxel Multiple Products Use of Hard-Coded Credentials (critical 9.8, exploited in the wild)
- [CVE-2020-9054](https://insights.sbomify.com/CVE-2020-9054/): Zyxel Multiple NAS Devices OS Command Injection (critical 9.8, exploited in the wild)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2023-33010 and fix it if it is affected.

What it is: CVE-2023-33010 is a critical memory corruption vulnerability in Zyxel ATP series firmware, published on 24 May 2023. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: Yes. Attackers have exploited CVE-2023-33010 in the wild since at least 5 Jun 2023.

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-2023-33010/ (Markdown: https://insights.sbomify.com/CVE-2023-33010/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2023-33010
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2023-33010
- OSV: https://osv.dev/vulnerability/CVE-2023-33010

---
From sbomify Insights: https://insights.sbomify.com/CVE-2023-33010/
Summaries are generated and may contain mistakes; the official description above is the record.