# CVE-2021-39183: Unsafe inline XSS Owncast

> Attackers can execute arbitrary JavaScript via pasted content in Owncast chat, potentially compromising user sessions.

- **Severity:** High 8.2 (`CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:H/A:L`)
- **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:** Yes
- **Published:** 14 Dec 2021
- **Updated:** 4 Aug 2024
- **Also known as:** GHSA-2hfj-cxw7-g45p, GO-2022-0291

## What is CVE-2021-39183?

CVE-2021-39183 is a high-severity cross-site scripting vulnerability in owncast, published on 14 Dec 2021. Any signed-in user can exploit it over the network, and only if a user opens a file or follows a link.

### Official description

Owncast is an open source, self-hosted live video streaming and chat server. In affected versions inline scripts are executed when Javascript is parsed via a paste action. This issue is patched in 0.0.9 by blocking unsafe-inline Content Security Policy and specifying the script-src. The worker-src is required to be set to blob for the video player.

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

## Which versions are affected by CVE-2021-39183?

3 open source packages ship an affected version, including github.com/owncast/owncast. It affects 1 product.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `github.com/owncast/owncast` | Go | All versions | 0.0.9 |
| `github.com/owncast/owncast` | Go | All versions | 0.0.9 |
| `github.com/owncast/owncast` | Go | All versions | 0.0.9 |

Products: Owncast Project Owncast.

## How do I fix CVE-2021-39183?

Upgrade github.com/owncast/owncast to 0.0.9 or later.

## Is CVE-2021-39183 being exploited?

There is no known exploitation of CVE-2021-39183 in the wild and no public exploit code.

## Other vulnerabilities in owncast

- [CVE-2023-46480](https://insights.sbomify.com/CVE-2023-46480/): OwnCast remote code execution vulnerability (critical 9.8)
- [CVE-2022-3751](https://insights.sbomify.com/CVE-2022-3751/): SQL Injection in owncast/owncast (high 8.8)
- [CVE-2023-3188](https://insights.sbomify.com/CVE-2023-3188/): Server-Side Request Forgery (SSRF) in owncast/owncast (high 8.3)
- [CVE-2024-29026](https://insights.sbomify.com/CVE-2024-29026/): Owncast cross origin request (high 8.2)
- [CVE-2024-31450](https://insights.sbomify.com/CVE-2024-31450/): Owncast vulnerable to arbitrary file deletion in emoji.go (GHSL-2023-277) (low 2.7)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2021-39183 and fix it if it is affected.

What it is: CVE-2021-39183 is a high-severity cross-site scripting vulnerability in owncast, published on 14 Dec 2021. 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-2021-39183 in the wild and no public exploit code.

Affected packages and fixed versions:
- github.com/owncast/owncast (Go): affected all versions; fixed in 0.0.9
- github.com/owncast/owncast (Go): affected all versions; fixed in 0.0.9
- github.com/owncast/owncast (Go): affected all versions; fixed in 0.0.9

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-2021-39183/ (Markdown: https://insights.sbomify.com/CVE-2021-39183/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-39183
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-39183
- OSV: https://osv.dev/vulnerability/CVE-2021-39183

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-39183/
Summaries are generated and may contain mistakes; the official description above is the record.