# CVE-2017-16876: mistune Cross-site scripting (XSS) vulnerability

> Remote attackers can inject arbitrary web script or HTML via the key argument in the Mistune Markdown parser library.

- **Severity:** Medium 6.1 (`CVSS:3.0/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:** Yes
- **Published:** 29 Dec 2017
- **Updated:** 5 Aug 2024
- **Also known as:** DEBIAN-CVE-2017-16876, GHSA-98gj-wwxm-cj3h, PYSEC-2017-18, UBUNTU-CVE-2017-16876

## What is CVE-2017-16876?

CVE-2017-16876 is a medium-severity cross-site scripting vulnerability in Fedoraproject Fedora, published on 29 Dec 2017. 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 in the _keyify function in mistune.py in Mistune before 0.8.1 allows remote attackers to inject arbitrary web script or HTML by leveraging failure to escape the "key" argument.

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

## Which versions are affected by CVE-2017-16876?

3 open source packages ship an affected version, including mistune. It affects 2 products.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `mistune` | PyPI | All versions | 0.8.1 |
| `mistune` | PyPI | All versions | 0.8.1 |
| `mistune` | PyPI | All versions | 0.8.1 |

Products: Fedoraproject Fedora, Mistune Project Mistune.

## How do I fix CVE-2017-16876?

Upgrade mistune to 0.8.1 or later.

## Is CVE-2017-16876 being exploited?

There is no known exploitation of CVE-2017-16876 in the wild and no public exploit code.

## Other vulnerabilities in Fedoraproject Fedora

- [CVE-2024-4577](https://insights.sbomify.com/CVE-2024-4577/): PHP-CGI OS Command Injection (critical 9.8, exploited in the wild)
- [CVE-2021-39226](https://insights.sbomify.com/CVE-2021-39226/): Grafana Authentication Bypass (critical 9.8, exploited in the wild)
- [CVE-2019-5544](https://insights.sbomify.com/CVE-2019-5544/): VMware ESXi and Horizon DaaS OpenSLP Heap-Based Buffer Overflow (critical 9.8, exploited in the wild)
- [CVE-2024-4947](https://insights.sbomify.com/CVE-2024-4947/): Google Chromium V8 Type Confusion (critical 9.6, exploited in the wild)
- [CVE-2024-4671](https://insights.sbomify.com/CVE-2024-4671/): Google Chromium Visuals Use-After-Free (critical 9.6, exploited in the wild)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2017-16876 and fix it if it is affected.

What it is: CVE-2017-16876 is a medium-severity cross-site scripting vulnerability in Fedoraproject Fedora, published on 29 Dec 2017. 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-2017-16876 in the wild and no public exploit code.

Affected packages and fixed versions:
- mistune (PyPI): affected all versions; fixed in 0.8.1
- mistune (PyPI): affected all versions; fixed in 0.8.1
- mistune (PyPI): affected all versions; fixed in 0.8.1

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-2017-16876/ (Markdown: https://insights.sbomify.com/CVE-2017-16876/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2017-16876
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2017-16876
- OSV: https://osv.dev/vulnerability/CVE-2017-16876

---
From sbomify Insights: https://insights.sbomify.com/CVE-2017-16876/
Summaries are generated and may contain mistakes; the official description above is the record.