Vulnerability Details CVE-2026-33347
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.
Exploit prediction scoring system (EPSS) score
EPSS Score 0.001
EPSS Ranking 17.8%
CVSS Severity
CVSS v3 Score 6.1
References
Products affected by CVE-2026-33347
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cpe:2.3:a:thephpleague:commonmark:*