# CVE-2021-40868: Cross-site scripting in n/a

> Reflected XSS in Cloudron login page allows attackers to execute scripts via the returnTo parameter, potentially leading to session hijacking.

- **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:** 21 Sep 2021
- **Updated:** 4 Aug 2024
- **Also known as:** GHSA-66gc-ch9m-r42v

## What is CVE-2021-40868?

CVE-2021-40868 is a medium-severity cross-site scripting vulnerability in n/a, published on 21 Sep 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

In Cloudron 6.2, the returnTo parameter on the login page is vulnerable to Reflected XSS.

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

## Which versions are affected by CVE-2021-40868?

It affects 1 product.


Products: Cloudron Cloudron.

## How do I fix CVE-2021-40868?

No fix has been published for CVE-2021-40868 yet. Limit exposure of the affected software until one is available.

## Is CVE-2021-40868 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2021-40868 exists.

Public exploit code:

- Cloudron 6.2 - 'returnTo ' Cross Site Scripting (Reflected) (exploitdb)
- Cloudron 6.2 Cross-Site Scripting (nuclei): http/cves/2021/CVE-2021-40868.yaml

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2021-40868 and fix it if it is affected.

What it is: CVE-2021-40868 is a medium-severity cross-site scripting vulnerability in n/a, published on 21 Sep 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: It is not confirmed as exploited in the wild, but public exploit code for CVE-2021-40868 exists.

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-2021-40868/ (Markdown: https://insights.sbomify.com/CVE-2021-40868/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-40868
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-40868
- OSV: https://osv.dev/vulnerability/CVE-2021-40868

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-40868/
Summaries are generated and may contain mistakes; the official description above is the record.