CVE-2026-33347
league/commonmark has an embed extension allowed_domains bypass
6.1
MEDIUM
CVSS 3.1
EPSS 0.24%
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.
How to fix CVE-2026-33347
To remediate CVE-2026-33347, upgrade the affected package to a fixed version below.
- —no fix listed
- —upgrade to 2.8.2 or later
Is CVE-2026-33347 being exploited?
Low — EPSS is 0.2%, meaning exploitation activity has not been observed at scale.
Affected packages (2)
- from 0
- >= 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 |