# CVE-2023-6397: Null dereference in ATP series firmware

> A LAN-based attacker can cause denial-of-service on Zyxel firewalls by triggering a null pointer dereference via a crafted RAR file when Anti-Malware is enabled.

- **Severity:** Medium 6.5 (`CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 20 Feb 2024
- **Updated:** 2 Aug 2024
- **Also known as:** GHSA-wj52-rfj4-xjcm

## What is CVE-2023-6397?

CVE-2023-6397 is a medium-severity vulnerability in Zyxel ATP series firmware, published on 20 Feb 2024. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

A null pointer dereference vulnerability in Zyxel ATP series firmware versions from 4.32 through 5.37 Patch 1 and USG FLEX series firmware versions from 4.50 through 5.37 Patch 1 could allow a LAN-based attacker to cause denial-of-service (DoS) conditions by downloading a crafted RAR compressed file onto a LAN-side host if the firewall has the “Anti-Malware” feature enabled.

Weakness: CWE-476 (NULL Pointer Dereference)

## Which versions are affected by CVE-2023-6397?

It affects 19 products.


Products: Zyxel Atp100 Firmware, Zyxel Atp100w Firmware, Zyxel Atp200 Firmware, Zyxel Atp500 Firmware, Zyxel Atp700 Firmware, Zyxel Atp800 Firmware, Zyxel Usg Flex 100 Firmware, Zyxel Usg Flex 100ax Firmware, Zyxel Usg Flex 100h Firmware, Zyxel Usg Flex 100w Firmware, Zyxel Usg Flex 200 Firmware, Zyxel Usg Flex 200h Firmware, Zyxel Usg Flex 200hp Firmware, Zyxel Usg Flex 500 Firmware, Zyxel Usg Flex 500h Firmware, Zyxel Usg Flex 50 Firmware, Zyxel Usg Flex 50w Firmware, Zyxel Usg Flex 700 Firmware, Zyxel Usg Flex 700h Firmware.

## How do I fix CVE-2023-6397?

No fix has been published for CVE-2023-6397 yet. Limit exposure of the affected software until one is available.

## Is CVE-2023-6397 being exploited?

There is no known exploitation of CVE-2023-6397 in the wild and no public exploit code.

## 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-2023-33010](https://insights.sbomify.com/CVE-2023-33010/): 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)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2023-6397 and fix it if it is affected.

What it is: CVE-2023-6397 is a medium-severity vulnerability in Zyxel ATP series firmware, published on 20 Feb 2024. 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-2023-6397 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-2023-6397/ (Markdown: https://insights.sbomify.com/CVE-2023-6397/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2023-6397
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2023-6397
- OSV: https://osv.dev/vulnerability/CVE-2023-6397

---
From sbomify Insights: https://insights.sbomify.com/CVE-2023-6397/
Summaries are generated and may contain mistakes; the official description above is the record.