# CVE-2021-4124: Cross-site Scripting (XSS) - Stored in meetecho/janus-gateway

> Stored XSS in Janus Gateway allows attackers to inject scripts, potentially leading to session hijacking or data theft.

- **Severity:** High 8.1 (`CVSS:3.0/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 16 Dec 2021
- **Updated:** 3 Aug 2024
- **Also known as:** DEBIAN-CVE-2021-4124, GHSA-gv3q-27qx-g2xh, UBUNTU-CVE-2021-4124

## What is CVE-2021-4124?

CVE-2021-4124 is a high-severity cross-site scripting vulnerability in meetecho/janus-gateway, published on 16 Dec 2021. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

janus-gateway is vulnerable to Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')

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

## Which versions are affected by CVE-2021-4124?

It affects 1 product.


Products: Meetecho Janus.

## How do I fix CVE-2021-4124?

No fix has been published for CVE-2021-4124 yet. Limit exposure of the affected software until one is available.

## Is CVE-2021-4124 being exploited?

There is no known exploitation of CVE-2021-4124 in the wild and no public exploit code.

## Other vulnerabilities in meetecho/janus-gateway

- [CVE-2020-14033](https://insights.sbomify.com/CVE-2020-14033/): Memory corruption in n/a (critical 9.8)
- [CVE-2020-14034](https://insights.sbomify.com/CVE-2020-14034/): Memory corruption in n/a (critical 9.8)
- [CVE-2020-13901](https://insights.sbomify.com/CVE-2020-13901/): Memory corruption in n/a (critical 9.8)
- [CVE-2020-10574](https://insights.sbomify.com/CVE-2020-10574/): Null dereference in n/a (critical 9.8)
- [CVE-2021-4020](https://insights.sbomify.com/CVE-2021-4020/): Cross-site Scripting (XSS) - Stored in meetecho/janus-gateway (high 8.8)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2021-4124 and fix it if it is affected.

What it is: CVE-2021-4124 is a high-severity cross-site scripting vulnerability in meetecho/janus-gateway, published on 16 Dec 2021. It can only be exploited from the same machine or local network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2021-4124 in the wild and no public exploit code.

Affected product: meetecho/janus-gateway. 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-2021-4124/ (Markdown: https://insights.sbomify.com/CVE-2021-4124/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-4124
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-4124
- OSV: https://osv.dev/vulnerability/CVE-2021-4124

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-4124/
Summaries are generated and may contain mistakes; the official description above is the record.