# CVE-2021-34821: Cross-site scripting in n/a

> Remote unauthenticated attackers can execute arbitrary scripts via XSS in the WebUI's 404 error handling by sending malicious requests to non-existing URIs.

- **Severity:** Medium 6.1 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** A user has to click or open something
- **Fix available:** No
- **Published:** 19 Jul 2021
- **Updated:** 4 Aug 2024
- **Also known as:** GHSA-c893-g5w3-m4cj

## What is CVE-2021-34821?

CVE-2021-34821 is a medium-severity cross-site scripting vulnerability in n/a, published on 19 Jul 2021. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.

### Official description

Cross Site Scripting (XSS) vulnerability exists in AAT Novus Management System through 1.51.2. The WebUI has wrong HTTP 404 error handling implemented. A remote, unauthenticated attacker may be able to exploit the issue by sending malicious HTTP requests to non-existing URIs. The value of the URL path filename is copied into the HTML document as plain text tags.

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

## Which versions are affected by CVE-2021-34821?

It affects 1 product.


Products: Aat Novus Management System.

## How do I fix CVE-2021-34821?

No fix has been published for CVE-2021-34821 yet. Limit exposure of the affected software until one is available.

## Is CVE-2021-34821 being exploited?

There is no known exploitation of CVE-2021-34821 in the wild and no public exploit code.

## Other vulnerabilities in n/a

- [CVE-2021-34820](https://insights.sbomify.com/CVE-2021-34820/): Path traversal in n/a (high 7.5)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2021-34821 and fix it if it is affected.

What it is: CVE-2021-34821 is a medium-severity cross-site scripting vulnerability in n/a, published on 19 Jul 2021. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.
Exploitation: There is no known exploitation of CVE-2021-34821 in the wild and no public exploit code.

Affected product: n/a. 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-2021-34821/ (Markdown: https://insights.sbomify.com/CVE-2021-34821/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-34821
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-34821
- OSV: https://osv.dev/vulnerability/CVE-2021-34821

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-34821/
Summaries are generated and may contain mistakes; the official description above is the record.