# CVE-2020-13821: Cross-site scripting in n/a

> Reflected XSS in HiveMQ Broker Control Center allows attackers to steal administrator session cookies via crafted MQTT packets.

- **Severity:** Medium 5.4 (`CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Over the internet
- **Victim action needed:** A user has to click or open something
- **Fix available:** No
- **Published:** 26 Aug 2020
- **Updated:** 4 Aug 2024
- **Also known as:** GHSA-9qcc-v828-vgx7

## What is CVE-2020-13821?

CVE-2020-13821 is a medium-severity cross-site scripting vulnerability in n/a, published on 26 Aug 2020. Any signed-in user can exploit it over the network, and only if a user opens a file or follows a link.

### Official description

An issue was discovered in HiveMQ Broker Control Center 4.3.2. A crafted clientid parameter in an MQTT packet (sent to the Broker) is reflected in the client section of the management console. The attacker's JavaScript is loaded in a browser, which can lead to theft of the session and cookie of the administrator's account of the Broker.

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

## Which versions are affected by CVE-2020-13821?

It affects 1 product.


Products: Hivemq Broker Control Center.

## How do I fix CVE-2020-13821?

No fix has been published for CVE-2020-13821 yet. Limit exposure of the affected software until one is available.

## Is CVE-2020-13821 being exploited?

There is no known exploitation of CVE-2020-13821 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2020-13821 and fix it if it is affected.

What it is: CVE-2020-13821 is a medium-severity cross-site scripting vulnerability in n/a, published on 26 Aug 2020. Any signed-in user can exploit it over the network, and only if a user opens a file or follows a link.
Exploitation: There is no known exploitation of CVE-2020-13821 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-2020-13821/ (Markdown: https://insights.sbomify.com/CVE-2020-13821/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2020-13821
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2020-13821
- OSV: https://osv.dev/vulnerability/CVE-2020-13821

---
From sbomify Insights: https://insights.sbomify.com/CVE-2020-13821/
Summaries are generated and may contain mistakes; the official description above is the record.