HTML Cleaner allows crafted scripts in special contexts like svg or math to pass through
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
Affected software
Click a technology to see all vulnerabilities affecting it.
| Platform | Package | Vulnerable versions | Fixed in |
|---|---|---|---|
| Python (PyPI) | lxml-html-clean | < 0.4.0 | 0.4.0 |
References
- https://github.com/fedora-python/lxml_html_clean/security/advisories/GHSA-5jfw-gq64-q45f
- https://github.com/fedora-python/lxml_html_clean/commit/c5d816f86eb3707d72a8ecf5f3823e0daa1b3808
- https://github.com/fedora-python/lxml_html_clean/pull/19
- https://nvd.nist.gov/vuln/detail/CVE-2024-52595
- https://github.com/fedora-python/lxml_html_clean
- https://github.com/pypa/advisory-database/tree/main/vulns/lxml-html-clean/PYSEC-2024-160.yaml
- CVSS vector
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:L/A:H- Weakness (CWE)
CWE-184, CWE-79, CWE-83- Platform
- Python (PyPI)
- Package
lxml-html-clean- Disclosed
- 19.11.2024
- Updated
- 11.10.2026 12:19
Sources and licenses
OSV / GitHub Advisory Database - PYSEC-2024-160 - PyPA Advisory Database; CC BY 4.0
OSV / GitHub Advisory Database - GHSA-5jfw-gq64-q45f - CC BY 4.0
Vulnerability history: lxml-html-clean
All published vulnerabilities of this package (Python (PyPI)), newest first. Shows whether this is a one-off slip or a package that needs watching.
- Total entries
- 4
- First → latest
- 11.2024 07.2026
- Without a fix
- 0
- Exploited in attacks
- 0
Severity breakdown
- High 2
- Medium 2
Disclosures per year
- 2024: 1
- 2025: 0
- 2026: 3
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HTML Cleaner allows crafted scripts in special contexts like svg or math to pass through this entry
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