HTML Cleaner allows crafted scripts in special contexts like svg or math to pass through
Date: 2024-11
Affected: pip/lxml-html-clean
Attack vector: xss
Category: vulnerability-disclosure
Severity: High
CVE: CVE-2024-52595
CWE: CWE-184
CWE-79
CWE-83
CVSS: 7.7 (CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:L/A:H)

### Impact The HTML Parser in lxml does not properly handle context-switching for special HTML tags such as `<svg>`, `<math>` and `<noscript>`. This behavior deviates from how web browsers parse and interpret such tags. Specifically, content in CSS comments is ignored by lxml_html_clean but may be interpreted differently by web browsers, enabling malicious scripts to bypass the cleaning process. This vulnerability could lead to Cross-Site Scripting (XSS) attacks, compromising the security of users relying on lxml_html_clean in default configuration for sanitizing untrusted HTML content. ### Patches Users employing the HTML cleaner in a security-sensitive context should upgrade to lxml 0.4.0, which addresses this issue. ### Workarounds As a temporary mitigation, users can configure lxml_html_clean with the following settings to prevent the exploitation of this vulnerability: * `remove_tags`: Specify tags to remove - their content is moved to their parents' tags. * `kill_tags`: Specify tags to be removed completely. * `allow_tags`: Restrict the set of permissible tags, excluding context-switching tags like `<svg>`, `<math>` and `<noscript>`. ### References * https://github.com/fedora-python/lxml_html_clean/pull/19 * https://github.com/fedora-python/lxml_html_clean/pull/19/commits/c5d816f86eb3707d72a8ecf5f3823e0daa1b3808


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Architectural layers (MAESTRO):