cvedb.io
CVE-2026-30838
MEDIUM · CVSS 6.1
EPSS exploitation probability: 0%
Published 2026-03-07T16:15:56.250 · Last modified 2026-06-17T10:33:00.337

Summary

league/commonmark is a PHP Markdown parser. Prior to version 2.8.1, the DisallowedRawHtml extension can be bypassed by inserting a newline, tab, or other ASCII whitespace character between a disallowed HTML tag name and the closing >. For example, <script\n> would pass through unfiltered and be rendered as a valid HTML tag by browsers. This is a cross-site scripting (XSS) vector for any application that relies on this extension to sanitize untrusted user input. All applications using the DisallowedRawHtml extension to process untrusted markdown are affected. Applications that use a dedicated HTML sanitizer (such as HTML Purifier) on the rendered output are not affected. This issue has been patched in version 2.8.1.

Affected products

thephpleague — commonmark

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References

This product uses data from the NVD API but is not endorsed or certified by the NVD. Informational only; not professional security advice.