CVE-2026-33347

EUVD-2026-20079
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.
Cross-site Scripting
ProviderTypeBase ScoreAtk. VectorAtk. ComplexityPriv. RequiredVector
NISTPrimary
6.1 MEDIUM
NETWORK
LOW
NONE
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
Base Score
CVSS 3.x
EPSS Score
Percentile: 15%
Affected Products (NVD)
VendorProductVersion
thephpleaguecommonmark
2.3.0 ≤
𝑥
< 2.8.2
𝑥
= Vulnerable software versions
Debian logo
Debian Releases
Debian Product
Codename
php-league-commonmark
bookworm
2.3.9-1+deb12u1
fixed
bullseye
postponed
forky
2.8.2-2
fixed
sid
2.8.2-2
fixed
trixie
2.7.0-1+deb13u1
fixed
Common Weakness Enumeration
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