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.
Advisories
Source ID Title
Github GHSA Github GHSA GHSA-hh8v-hgvp-g3f5 league/commonmark has an embed extension allowed_domains bypass
Fixes

Solution

No solution given by the vendor.


Workaround

No workaround given by the vendor.

History

Tue, 24 Mar 2026 19:45:00 +0000

Type Values Removed Values Added
Description 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.
Title league/commonmark has an embed extension allowed_domains bypass
Weaknesses CWE-185
CWE-79
CWE-918
References
Metrics cvssV4_0

{'score': 6.3, 'vector': 'CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:L/VA:N/SC:L/SI:L/SA:N'}


Projects

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cve-icon MITRE

Status: PUBLISHED

Assigner: GitHub_M

Published:

Updated: 2026-03-24T19:26:23.872Z

Reserved: 2026-03-18T22:15:11.814Z

Link: CVE-2026-33347

cve-icon Vulnrichment

No data.

cve-icon NVD

Status : Received

Published: 2026-03-24T20:16:29.240

Modified: 2026-03-24T20:16:29.240

Link: CVE-2026-33347

cve-icon Redhat

No data.

cve-icon OpenCVE Enrichment

No data.

Weaknesses