CVE-2026-33347

league/commonmark is a PHP Markdown parser. From version 2.3.0 to before version 2.8.2, the DomainFilteringAdapter in the Embed extension is vulnerable to an allowlist bypass due to a missing hostname boundary assertion in the domain-matching regex. An attacker-controlled domain like youtube.com.evil passes the allowlist check when youtube.com is an allowed domain. This issue has been patched in version 2.8.2.

Score

CVSS 4.0 6.3 Medium

Status

Analyzed - security-advisories@github.com

Published

2026-03-24

Last modified

2026-03-26

Weaknesses

CWE-185, CWE-79, CWE-918

Affected products

• Commonmark (Thephpleague)

References

• https://github.com/thephpleague/commonmark/commit/59fb075d2101740c337c7216e3f32b36c204218b
• https://github.com/thephpleague/commonmark/releases/tag/2.8.2
• https://github.com/thephpleague/commonmark/security/advisories/GHSA-hh8v-hgvp-g3f5