CVE-2026-30838
Publication date 7 March 2026
Last updated 10 July 2026
Ubuntu priority
Description
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.
Status
| Package | Ubuntu Release | Status |
|---|---|---|
| php-league-commonmark | 26.04 LTS resolute |
Vulnerable
|
| 24.04 LTS noble |
Fixed 2.4.2-2ubuntu0.1~esm1
|
|
| 22.04 LTS jammy |
Fixed 1.6.7-1ubuntu0.1~esm1
|
|
| 20.04 LTS focal |
Fixed 1.3.1-1ubuntu2+esm1
|
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CVSS version:
Base score
5.1 · Medium
Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:P/VC:N/VI:L/VA:N/SC:L/SI:L/SA:N
Base score
6.1 · Medium
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
References
Related Ubuntu Security Notices (USN)
- USN-8194-1
- league/commonmark vulnerabilities
- 21 April 2026