# CVE-2021-34343: Buffer Overflow Vulnerability in QTS, QuTS hero, and QuTScloud

> Attackers can execute arbitrary code via a stack buffer overflow in QNAP NAS operating systems, requiring immediate firmware updates.

- **Severity:** Medium 6.0 (`CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:L/I:L/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** An administrator
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 10 Sep 2021
- **Updated:** 16 Sep 2024
- **Also known as:** GHSA-h5w8-c4g8-8ch6

## What is CVE-2021-34343?

CVE-2021-34343 is a medium-severity memory corruption vulnerability in Qnap Qts, published on 10 Sep 2021. An attacker needs administrator access to exploit it, with no action from the victim.

### Official description

A stack buffer overflow vulnerability has been reported to affect QNAP device running QTS, QuTScloud, QuTS hero. If exploited, this vulnerability allows attackers to execute arbitrary code. We have already fixed this vulnerability in the following versions of QTS, QuTScloud, QuTS hero: QTS 4.5.4.1715 build 20210630 and later QTS 5.0.0.1716 build 20210701 and later QuTScloud c4.5.6.1755 and later QuTS hero h4.5.4.1771 build 20210825 and later

Weakness: CWE-787 (Out-of-bounds Write)

## Which versions are affected by CVE-2021-34343?

It affects 3 products.


Products: Qnap Qts, Qnap Quts Hero, Qnap Qutscloud.

## How do I fix CVE-2021-34343?

No fix has been published for CVE-2021-34343 yet. Limit exposure of the affected software until one is available.

## Is CVE-2021-34343 being exploited?

There is no known exploitation of CVE-2021-34343 in the wild and no public exploit code.

## Other vulnerabilities in Qnap Qts

- [CVE-2020-2509](https://insights.sbomify.com/CVE-2020-2509/): QNAP Network-Attached Storage (NAS) Command Injection (critical 9.8, exploited in the wild)
- [CVE-2018-19949](https://insights.sbomify.com/CVE-2018-19949/): QNAP NAS File Station Command Injection (critical 9.8, exploited in the wild)
- [CVE-2019-7193](https://insights.sbomify.com/CVE-2019-7193/): QNAP QTS Improper Input Validation (critical 9.8, exploited in the wild)
- [CVE-2018-19943](https://insights.sbomify.com/CVE-2018-19943/): QNAP NAS File Station Cross-Site Scripting (high 8.0, exploited in the wild)
- [CVE-2018-19953](https://insights.sbomify.com/CVE-2018-19953/): QNAP NAS File Station Cross-Site Scripting (medium 6.1, exploited in the wild)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2021-34343 and fix it if it is affected.

What it is: CVE-2021-34343 is a medium-severity memory corruption vulnerability in Qnap Qts, published on 10 Sep 2021. An attacker needs administrator access to exploit it, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2021-34343 in the wild and no public exploit code.

Affected product: Qnap Qts. 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-2021-34343/ (Markdown: https://insights.sbomify.com/CVE-2021-34343/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-34343
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-34343
- OSV: https://osv.dev/vulnerability/CVE-2021-34343

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-34343/
Summaries are generated and may contain mistakes; the official description above is the record.