Moderate severity vulnerability that affects league/commonmark

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

6.1 · CVSS:3.0/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N

EPSS

• CVE-2019-10010: 1.05% estimated exploitation activity in the next 30 days; percentile 64.31 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

CVE-2019-10010 Impact In league/commonmark 0.18.2 and below, malicious users can insert double-encoded HTML entities into their Markdown like this: This library would (correctly) unescape the & entity to & during the parsing step. However, the renderer step would fail to properly re-escape the resulting : string, thus producing the following malicious HTML output: Browsers would interpret : as a : character and allow the JS to be executed when the link is clicked. This vulnerability was present in the upstream library this project was forked from and therefore exists in all prior versions of league/commonmark. Solution The new 0.18.3 release mirrors the fix made upstream - we no longer attempt to preserve entities when rendering HTML attributes like href, src, title, etc. The $preserveEntities parameter of Xml::escape() is therefore no longer used internally, so it has been deprecated and marked for removal in the next major release (0.19.0). Credits - Mohit Fawaz for…

Published by the source

17 Sep 2019, 22:47 UTC

Last modified by the source

6 Feb 2024, 13:16 UTC

Source last checked

26 Oct 2026, 14:15 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-3v43-877x-qgmq

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# Patch Next advisory brief: CVE-2019-10010

Advisory: Moderate severity vulnerability that affects league/commonmark
IDs: CVE-2019-10010, GHSA-3v43-877x-qgmq
Record: https://patchnext.com/advisories/cve-2019-10010 (revision 1, source checked 26 Oct 2026, 14:15 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 6.1)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: league/commonmark 0.18.3. A vendor fix does not mean a deployment is fixed.

## Affected components
- Packagist league/commonmark: affected < 0.18.3; fixed in 0.18.3

## Suggested inspection (read-only)
- Packagist league/commonmark: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on league/commonmark.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-3v43-877x-qgmq (GitHub-reviewed advisory GHSA-3v43-877x-qgmq lists affected ranges: Packagist league/commonmark >=0 <0.18.3)

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