CVE-2026-33347

MEDIUM

league/commonmark has an embed extension allowed_domains bypass

Title source: cna

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.

References (3)

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

[X_Refsource_Misc] https://github.com/thephpleague/commonmark/commit/59fb075d2101740c337c7216e3f32b36c204218b

View Writeup ZIP pw:eip

[X_Refsource_Misc] https://github.com/thephpleague/commonmark/releases/tag/2.8.2

Scores

CVSS v3 6.1

EPSS 0.0001

EPSS Percentile 1.7%

Attack Vector NETWORK

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N

Details

CWE

CWE-185 CWE-79 CWE-918

Status published

Products (3)

league/commonmark 2.3.0 - 2.8.2Packagist

thephpleague/commonmark 2.3.0 - 2.8.2

thephpleague/commonmark >= 2.3.0, < 2.8.2

Published Mar 24, 2026

Tracked Since Mar 25, 2026