CVE-2025-46734: medium-severity vulnerability in thephpleague commonmark
league/commonmark Cross-site Scripting vulnerability in Attributes extension
Published · Updated
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13Vexday Risk Score
No sign of exploitation. No public exploitation artifact known so far.
ssvc Trackcvss 6.4epss 0.4%
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.
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:L/I:L/A:N
Affected products
thephpleague · commonmarkRelated CVEs — thephpleague commonmark
In the same product, most dangerous first.
CVE-2026-71488HIGHleague/commonmark: Quadratic-time denial of service when parsing crafted MarkdownEPSS 0.6%CVE-2026-86429HIGHcommonmark before 2.9.1 Denial of Service via SmartPunct and AttributesEPSS 0.5%CVE-2026-86434HIGHcommonmark 2.0.0 through 2.8.3 Denial of Service via Slug CollisionEPSS 0.5%CVE-2026-86433HIGHcommonmark 1.5.0 before 2.8.4 Denial of Service via AttributesEPSS 0.5%CVE-2026-86430HIGHleague/commonmark before 2.9.1 Denial of Service via parsingEPSS 0.5%CVE-2026-86428HIGHcommonmark 1.5.0 before 2.10.0 Denial of Service via AttributesEPSS 0.5%