USN-8194-1: league/commonmark vulnerabilities

Publication date

21 April 2026

Overview

Several security issues were fixed in league/commonmark.


Packages

  • php-league-commonmark - Highly-extensible PHP Markdown parser which fully supports the CommonMark and GFM specs

Details

It was discovered that league/commonmark did not properly restrict
unsafe attributes when the Attributes extension was enabled. An attacker
could possibly use this issue to cause cross-site scripting by injecting
malicious code into rendered HTML. This issue only affected Ubuntu 22.04
LTS and Ubuntu 24.04 LTS. (CVE-2025-46734)

It was discovered that league/commonmark did not properly block certain
disallowed HTML tags in some cases. An attacker could possibly use this
issue to cause cross-site scripting by inserting malicious HTML that
bypassed filtering. (CVE-2026-30838)

It was discovered that league/commonmark did not properly enforce domain
allowlist checks in the Embed extension. An attacker could possibly use
this issue to bypass domain restrictions and cause untrusted content to
be treated as allowed. This issue only affected Ubuntu 24.04...

It was discovered that league/commonmark did not properly restrict
unsafe attributes when the Attributes extension was enabled. An attacker
could possibly use this issue to cause cross-site scripting by injecting
malicious code into rendered HTML. This issue only affected Ubuntu 22.04
LTS and Ubuntu 24.04 LTS. (CVE-2025-46734)

It was discovered that league/commonmark did not properly block certain
disallowed HTML tags in some cases. An attacker could possibly use this
issue to cause cross-site scripting by inserting malicious HTML that
bypassed filtering. (CVE-2026-30838)

It was discovered that league/commonmark did not properly enforce domain
allowlist checks in the Embed extension. An attacker could possibly use
this issue to bypass domain restrictions and cause untrusted content to
be treated as allowed. This issue only affected Ubuntu 24.04 LTS.
(CVE-2026-33347)


Update instructions

In general, a standard system update will make all the necessary changes.

Learn more about how to get the fixes.

The problem can be corrected by updating your system to the following package versions:

Ubuntu Release Package Version
24.04 LTS noble php-league-commonmark –  2.4.2-2ubuntu0.1~esm1  
22.04 LTS jammy php-league-commonmark –  1.6.7-1ubuntu0.1~esm1  
20.04 LTS focal php-league-commonmark –  1.3.1-1ubuntu2+esm1  

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