# CVE-2019-10010: Moderate severity vulnerability that affects league/commonmark

> Remote attackers can inject malicious scripts via double-encoded HTML entities in the PHP League CommonMark library, potentially compromising user sessions.

- **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:** 24 Mar 2019
- **Updated:** 4 Aug 2024
- **Also known as:** GHSA-3v43-877x-qgmq

## What is CVE-2019-10010?

CVE-2019-10010 is a medium-severity cross-site scripting vulnerability in n/a, published on 24 Mar 2019. 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 PHP League CommonMark library before 0.18.3 allows remote attackers to insert unsafe links into HTML by using double-encoded HTML entities that are not properly escaped during rendering, a different vulnerability than CVE-2018-20583.

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

## Which versions are affected by CVE-2019-10010?

2 open source packages ship an affected version, including league/commonmark. It affects 1 product.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `league/commonmark` | Packagist | All versions | 0.18.3 |
| `league/commonmark` | Packagist | All versions | 0.18.3 |

Products: Thephpleague Commonmark.

## How do I fix CVE-2019-10010?

Upgrade league/commonmark to 0.18.3 or later.

## Is CVE-2019-10010 being exploited?

There is no known exploitation of CVE-2019-10010 in the wild and no public exploit code.

## Other vulnerabilities in n/a

- [CVE-2026-86428](https://insights.sbomify.com/CVE-2026-86428/): commonmark 1.5.0 before 2.10.0 Denial of Service via Attributes (high 8.7)
- [CVE-2026-86429](https://insights.sbomify.com/CVE-2026-86429/): commonmark before 2.9.1 Denial of Service via SmartPunct and Attributes (high 8.7)
- [CVE-2026-86430](https://insights.sbomify.com/CVE-2026-86430/): league/commonmark before 2.9.1 Denial of Service via parsing (high 8.7)
- [CVE-2026-86431](https://insights.sbomify.com/CVE-2026-86431/): commonmark before 2.9.1 XSS via AttributesExtension form feed bypass (medium 6.9)
- [CVE-2026-33347](https://insights.sbomify.com/CVE-2026-33347/): league/commonmark has an embed extension allowed_domains bypass (medium 6.3)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2019-10010 and fix it if it is affected.

What it is: CVE-2019-10010 is a medium-severity cross-site scripting vulnerability in n/a, published on 24 Mar 2019. 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-2019-10010 in the wild and no public exploit code.

Affected packages and fixed versions:
- league/commonmark (Packagist): affected all versions; fixed in 0.18.3
- league/commonmark (Packagist): affected all versions; fixed in 0.18.3

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-2019-10010/ (Markdown: https://insights.sbomify.com/CVE-2019-10010/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2019-10010
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2019-10010
- OSV: https://osv.dev/vulnerability/CVE-2019-10010

---
From sbomify Insights: https://insights.sbomify.com/CVE-2019-10010/
Summaries are generated and may contain mistakes; the official description above is the record.