# CVE-2026-28348: lxml-html-clean has CSS @import Filter Bypass via Unicode Escapes

Source: https://junglewise.ai/threats/cve-2026-28348-lxml-html-clean-has-css-import-filter-bypass-via-unicode-escapes  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-03-05  
License: CC BY 4.0 with a link back

CVE-2026-28348 · Severity: low · CVSS 3.1 · Published 2026-03-05

lxml_html_clean is a project for HTML cleaning functionalities copied from `lxml.html.clean`. Prior to version 0.4.4, the _has_sneaky_javascript() method strips backslashes before checking for dangerous CSS keywords. This causes CSS Unicode escape sequences to bypass the @import and expression() filters, allowing external CSS loading or XSS in older browsers. This issue has been patched in version 0.4.4.

Technologies: [lxml_html_clean (PyPI)](https://junglewise.ai/threats/technologies/lxml-html-clean). Vendors: [PyPI](https://junglewise.ai/threats/vendors/pypi).

## Quick answers

**Is CVE-2026-28348 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-28348 being exploited in the wild.

**How severe is CVE-2026-28348?** Low severity, with a CVSS score of 3.1, published 5 March 2026.

**Which products and versions are affected?** lxml_html_clean (PyPI) ECOSYSTEM:introduced=0,fixed=0.4.4.

**Is there a fix for CVE-2026-28348?** Yes. lxml_html_clean (PyPI): upgrade to 0.4.4 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**Am I affected by CVE-2026-28348?** Check whether you run lxml_html_clean (PyPI) at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## How to fix

- lxml_html_clean (PyPI): upgrade to 0.4.4 or later

  ```sh
  pip install "lxml_html_clean>=0.4.4"
  ```


## Affected products

- lxml_html_clean (PyPI) ECOSYSTEM:introduced=0,fixed=0.4.4

## Identifiers

- CVE-2026-28348
- GHSA-hw26-mmpg-fqfg
- PYSEC-2026-2201

## Related threats

- [lxml_html_clean XSS via xlink:href namespaced URL attributes](https://junglewise.ai/threats/cve-2026-49825-lxml-html-clean-xss-via-xlink-href-namespaced-url-attributes)
- [lxml-html-clean has <base> tag injection through default Cleaner configuration](https://junglewise.ai/threats/cve-2026-28350-lxml-html-clean-has-base-tag-injection-through-default-cleaner)
- [HTML Cleaner allows crafted scripts in special contexts like svg or math to pass through](https://junglewise.ai/threats/cve-2024-52595-html-cleaner-allows-crafted-scripts-in-special-contexts-like-svg)