{"id":"UBUNTU-CVE-2025-46734","details":"league/commonmark is a PHP Markdown parser. A cross-site scripting (XSS) vulnerability in the Attributes extension of the league/commonmark library (versions 1.5.0 through 2.6.x) allows remote attackers to insert malicious JavaScript calls into HTML. The league/commonmark library provides configuration options such as `html_input: 'strip'` and `allow_unsafe_links: false` to mitigate cross-site scripting (XSS) attacks by stripping raw HTML and disallowing unsafe links. However, when the Attributes Extension is enabled, it introduces a way for users to inject arbitrary HTML attributes into elements via Markdown syntax using curly braces. Version 2.7.0 contains three changes to prevent this XSS attack vector: All attributes starting with `on` are considered unsafe and blocked by default; support for an explicit allowlist of allowed HTML attributes; and manually-added `href` and `src` attributes now respect the existing `allow_unsafe_links` configuration option. If upgrading is not feasible, please consider disabling the `AttributesExtension` for untrusted users and/or filtering the rendered HTML through a library like HTMLPurifier.","modified":"2026-04-27T19:10:38.329729Z","published":"2025-05-05T20:15:00Z","related":["USN-8194-1"],"upstream":["CVE-2025-46734"],"references":[{"type":"REPORT","url":"https://ubuntu.com/security/CVE-2025-46734"},{"type":"REPORT","url":"https://www.cve.org/CVERecord?id=CVE-2025-46734"},{"type":"REPORT","url":"https://github.com/thephpleague/commonmark/commit/f0d626cf05ad3e99e6db26ebcb9091b6cd1cd89b"},{"type":"REPORT","url":"https://github.com/thephpleague/commonmark/security/advisories/GHSA-3527-qv2q-pfvx"},{"type":"ADVISORY","url":"https://ubuntu.com/security/notices/USN-8194-1"}],"affected":[{"package":{"name":"php-league-commonmark","ecosystem":"Ubuntu:Pro:20.04:LTS","purl":"pkg:deb/ubuntu/php-league-commonmark@1.3.1-1ubuntu2+esm1?arch=source&distro=esm-apps/focal"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"1.3.1-1ubuntu2+esm1"}]}],"versions":["1.1.2-1","1.2.0-1","1.3.0-1","1.3.1-1","1.3.1-1ubuntu2"],"ecosystem_specific":{"availability":"Available with Ubuntu Pro: https://ubuntu.com/pro","binaries":[{"binary_name":"php-league-commonmark","binary_version":"1.3.1-1ubuntu2+esm1"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2025/UBUNTU-CVE-2025-46734.json"}},{"package":{"name":"php-league-commonmark","ecosystem":"Ubuntu:Pro:22.04:LTS","purl":"pkg:deb/ubuntu/php-league-commonmark@1.6.7-1ubuntu0.1~esm1?arch=source&distro=esm-apps/jammy"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"1.6.7-1ubuntu0.1~esm1"}]}],"versions":["1.5.7-2build1","1.6.6-1build1","1.6.7-1"],"ecosystem_specific":{"availability":"Available with Ubuntu Pro: https://ubuntu.com/pro","binaries":[{"binary_name":"php-league-commonmark","binary_version":"1.6.7-1ubuntu0.1~esm1"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2025/UBUNTU-CVE-2025-46734.json"}},{"package":{"name":"php-league-commonmark","ecosystem":"Ubuntu:Pro:24.04:LTS","purl":"pkg:deb/ubuntu/php-league-commonmark@2.4.2-2ubuntu0.1~esm1?arch=source&distro=esm-apps/noble"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"2.4.2-2ubuntu0.1~esm1"}]}],"versions":["2.3.9-1","2.4.1-1","2.4.2-1","2.4.2-2"],"ecosystem_specific":{"availability":"Available with Ubuntu Pro: https://ubuntu.com/pro","binaries":[{"binary_name":"php-league-commonmark","binary_version":"2.4.2-2ubuntu0.1~esm1"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2025/UBUNTU-CVE-2025-46734.json"}}],"schema_version":"1.7.5","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:L/I:L/A:N"},{"type":"Ubuntu","score":"medium"}]}