XSS Vulnerability in PHP Markdown Parser of League/CommonMark
CVE-2025-46734

6.4MEDIUM

Key Information:

Vendor

ThePHPleague

Status
Commonmark
Vendor
CVE Published:
5 May 2025

What is CVE-2025-46734?

A cross-site scripting (XSS) vulnerability exists in the Attributes extension of the league/commonmark library, allowing remote attackers to embed malicious JavaScript into HTML. This issue affects versions 1.5.0 through 2.6.x, facilitating the injection of unsafe HTML attributes through Markdown syntax. While the library offers configuration options to mitigate XSS attacks, enabling the Attributes Extension may expose users to risks. Version 2.7.0 introduces improvements to address this vulnerability by blocking unsafe attributes and enforcing a whitelist for allowed HTML attributes. To enhance security, it is advised to either upgrade or disable the AttributesExtension for untrusted users, and consider filtering rendered HTML using libraries like HTMLPurifier.

Affected Version(s)

commonmark < 2.7.0

References

https://github.com/thephpleague/commonmark/security/advis...
x_refsource_CONFIRM
https://github.com/thephpleague/commonmark/commit/f0d626c...
x_refsource_MISC

CVSS V3.1

Score:
6.4
Severity:
MEDIUM
Confidentiality:
Low
Integrity:
Low
Availability:
Low
Attack Vector:
Network
Attack Complexity:
Low
Privileges Required:
Low
User Interaction:
None
Scope:
Changed

Timeline

  • Vulnerability published

  • Vulnerability Reserved

.