CVE-2026-33347
MEDIUM6.1EPSS 0.01%league/commonmark has an embed extension allowed_domains bypass
Published: 3/19/2026Modified: 5/27/2026
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.
Affected packages (2)
- Debian/php-league-commonmarkfrom 0
- Packagist/league/commonmark>= 2.3.0, < 2.8.2
CVSS scores
| Source | Version | Severity | Vector |
|---|---|---|---|
| osv | CVSS 4.0 | — | 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 |
| osv | CVSS 3.1 | MEDIUM6.1 | CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N |
References (6)
- ADVISORYhttps://nvd.nist.gov/vuln/detail/CVE-2026-33347
- ADVISORYhttps://security-tracker.debian.org/tracker/CVE-2026-33347
- PATCHhttps://github.com/thephpleague/commonmark
- WEBhttps://github.com/thephpleague/commonmark/commit/59fb075d2101740c337c7216e3f32b36c204218b
- WEBhttps://github.com/thephpleague/commonmark/releases/tag/2.8.2
- WEBhttps://github.com/thephpleague/commonmark/security/advisories/GHSA-hh8v-hgvp-g3f5