CVE-2026-33347

MEDIUM6.3

league/commonmark has an embed extension allowed_domains bypass

Published Mar 24, 2026

Modified 1 months ago

Details

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.

References

WEB

https://github.com/thephpleague/commonmark/commit/59fb075d2101740c337c7216e3f32b36c204218b

WEB

https://github.com/thephpleague/commonmark/releases/tag/2.8.2

WEB

https://github.com/thephpleague/commonmark/security/advisories/GHSA-hh8v-hgvp-g3f5

ADVISORY

https://www.cve.org/CVERecord?id=CVE-2026-33347

CVSS Analysis

CVSS v4.0

6.3