# CVE-2021-34359: Stored XSS Vulnerability in Proxy Server

> Remote attackers can inject malicious code via stored XSS in QNAP Proxy Server, potentially compromising user sessions or data.

- **Severity:** Medium 6.9 (`CVSS:3.1/AV:N/AC:L/PR:H/UI:R/S:C/C:H/I:L/A:N`)
- **Exploited in the wild:** Not known
- **Login needed:** An administrator
- **Attackable:** Over the internet
- **Victim action needed:** A user has to click or open something
- **Fix available:** No
- **Published:** 25 Feb 2022
- **Updated:** 17 Sep 2024
- **Also known as:** GHSA-2cm8-2mh8-q729

## What is CVE-2021-34359?

CVE-2021-34359 is a medium-severity cross-site scripting vulnerability in QNAP Systems Inc. Proxy Server, published on 25 Feb 2022. An attacker needs administrator access to exploit it, and only if a user opens a file or follows a link.

### Official description

A cross-site scripting (XSS) vulnerability has been reported to affect QNAP device running Proxy Server. If exploited, this vulnerability allows remote attackers to inject malicious code. We have already fixed this vulnerability in the following versions of Proxy Server: QTS 4.5.x: Proxy Server 1.4.2 ( 2021/12/30 ) and later

Weakness: CWE-79 (Improper Neutralization of Input During Web Page Generation)

## Which versions are affected by CVE-2021-34359?

It affects 1 product.


Products: Qnap Nas Proxy Server.

## How do I fix CVE-2021-34359?

No fix has been published for CVE-2021-34359 yet. Limit exposure of the affected software until one is available.

## Is CVE-2021-34359 being exploited?

There is no known exploitation of CVE-2021-34359 in the wild and no public exploit code.

## Other vulnerabilities in QNAP Systems Inc. Proxy Server

- [CVE-2017-7637](https://insights.sbomify.com/CVE-2017-7637/): Command injection in n/a (critical 9.8)
- [CVE-2017-7635](https://insights.sbomify.com/CVE-2017-7635/): Cross-site request forgery in n/a (high 8.8)
- [CVE-2017-7636](https://insights.sbomify.com/CVE-2017-7636/): Cross-site scripting in n/a (medium 6.1)
- [CVE-2021-34360](https://insights.sbomify.com/CVE-2021-34360/): CSRF Bypass in Proxy Server (medium 5.3)
- [CVE-2021-34361](https://insights.sbomify.com/CVE-2021-34361/): Reflected XSS Vulnerability in Proxy Server (medium 5.3)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2021-34359 and fix it if it is affected.

What it is: CVE-2021-34359 is a medium-severity cross-site scripting vulnerability in QNAP Systems Inc. Proxy Server, published on 25 Feb 2022. An attacker needs administrator access to exploit it, and only if a user opens a file or follows a link.
Exploitation: There is no known exploitation of CVE-2021-34359 in the wild and no public exploit code.

Affected product: QNAP Systems Inc. Proxy Server. 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-2021-34359/ (Markdown: https://insights.sbomify.com/CVE-2021-34359/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-34359
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-34359
- OSV: https://osv.dev/vulnerability/CVE-2021-34359

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-34359/
Summaries are generated and may contain mistakes; the official description above is the record.