# CVE-2021-28798: Relative Path Traversal Vulnerability in QTS and QuTS hero

> Attackers can exploit a relative path traversal flaw in QNAP NAS firmware to modify system files, compromising system integrity.

- **Severity:** High 8.8 (`CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H`)
- **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:** 21 May 2021
- **Updated:** 16 Sep 2024
- **Also known as:** GHSA-hc4v-wrjp-6qpg

## What is CVE-2021-28798?

CVE-2021-28798 is a high-severity path traversal vulnerability in Qnap Qts, published on 21 May 2021. Any signed-in user can exploit it over the network, with no action from the victim.

### Official description

A relative path traversal vulnerability has been reported to affect QNAP NAS running QTS and QuTS hero. If exploited, this vulnerability allows attackers to modify files that impact system integrity. QNAP have already fixed this vulnerability in the following versions: QTS 4.5.2.1630 Build 20210406 and later QTS 4.3.6.1663 Build 20210504 and later QTS 4.3.3.1624 Build 20210416 and later QuTS hero h4.5.2.1638 Build 20210414 and later QNAP NAS running QTS 4.5.3 are not affected.

Weakness: CWE-22 (Improper Limitation of a Pathname to a Restricted Directory), CWE-284 (Improper Access Control), CWE-23 (Relative Path Traversal)

## Which versions are affected by CVE-2021-28798?

It affects 2 products.


Products: Qnap Qts, Qnap Quts Hero.

## How do I fix CVE-2021-28798?

No fix has been published for CVE-2021-28798 yet. Limit exposure of the affected software until one is available.

## Is CVE-2021-28798 being exploited?

There is no known exploitation of CVE-2021-28798 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-2021-28798 and fix it if it is affected.

What it is: CVE-2021-28798 is a high-severity path traversal vulnerability in Qnap Qts, published on 21 May 2021. Any signed-in user can exploit it over the network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2021-28798 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-2021-28798/ (Markdown: https://insights.sbomify.com/CVE-2021-28798/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-28798
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-28798
- OSV: https://osv.dev/vulnerability/CVE-2021-28798

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-28798/
Summaries are generated and may contain mistakes; the official description above is the record.