CVE-2026-33347CWE-185CWE-79CWE-918

league/commonmark has an embed extension allowed_domains bypass

Medium · published March 24, 2026

CVSS v4.0
6.3
EPSS
0%
Percentile
24.8
In the wild
Unconfirmed
What it is

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.

The record
Technical detail
CVSS v4.0
6.3 · MEDIUM
Vector
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
EPSS
0.00329 · 24.8th percentile
Weaknesses
CWE-185 · Incorrect Regular Expression; CWE-79 · Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting'); CWE-918 · Server-Side Request Forgery (SSRF)
Published
2026-03-24T19:26Z
EPSS history
Timeline
  • 24 MAR 19:26Z
    league/commonmark has an embed extension allowed_domains bypass
    cvelistv5