lxml_html_clean: CSS @import Filter Bypass via Unicode Escapes
Priority MEDIUM 60CWE-116Published · Updated
Key facts
- Attack vector
- Network
- Privileges required
- None
- User interaction
- Required
- Attack complexity
- Low
- Impact type
- —
- Confidentiality · integrity · availability
- Low · Low · None
- Fix status
- Fixed
Attack profile from CVSS 3.1 · CNA. Fix status from CNA and GitHub.
Summary
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.
Why it matters now
Exploitation Proof of concept CISA SSVC · not in CISA KEV
EPSS 0.00282 20th percentileScored 2026-11-07
Public exploit Yes 1 exploit referenceTagged by NVD
Fix Fixed lxml_html_clean (fedora-python): 0.4.4lxml-html-clean (PyPI): 0.4.4
SSVC decision points
CISA ADP · SSVC 2.0.3
- Exploitation
- Poc
- Automatable
- No
- Technical impact
- Partial
The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.
Affected products
| Vendor | Product | Affected versions | Fixed in | Status | Source |
|---|---|---|---|---|---|
| fedora-python | lxml_html_clean | before 0.4.4 | 0.4.4 | Patch available | CNA |
| — | lxml-html-clean (PyPI) | before 0.4.4 | 0.4.4 | Patch available | GHSA-hw26-mmpg-fqfg |
- lxml_html_clean Vendorfedora-python Affected before 0.4.4 Fixed in 0.4.4 Patch available CNA
- lxml-html-clean (PyPI) Vendor— Affected before 0.4.4 Fixed in 0.4.4 Patch available GHSA-hw26-mmpg-fqfg
CPE configurations NVD · 1
| CPE | Versions | Role | Vendor |
|---|---|---|---|
| cpe:2.3:a:fedoralovespython:lxml_html_clean:*:*:*:*:*:python:*:* | before 0.4.4 | Vulnerable | fedora-python |
- cpe:2.3:a:fedoralovespython:lxml_html_clean:*:*:*:*:*:python:*:* Versions before 0.4.4 Vulnerable ·fedora-python
Remediation
- Fix · CNA lxml_html_clean (fedora-python) Fixed in 0.4.4
- Fix · GHSA-hw26-mmpg-fqfg lxml-html-clean (PyPI) Fixed in 0.4.4 Advisory →
Vendor assessments
Timeline
- 2026-10-02 Threatist record created from CVE-2026-28348
- 2026-10-03 Alias added: GHSA-hw26-mmpg-fqfg
References
Patch 1
More fedora-python Lxml Html Clean vulnerabilities
- TI-2026-22630 lxml_html_clean: <base> tag injection through default Cleaner configuration CVSS 3.1MEDIUM 6.1
- TI-2024-35255 HTML Cleaner allows crafted scripts in special contexts like svg or math to pass through CVSS 3.1HIGH 7.7
Sources
- CVE-2026-28348 · CVE Program
- CVE-2026-28348 · NVD
- FIRST EPSS
- GHSA-hw26-mmpg-fqfg · GitHub Advisory Database · CC BY 4.0
- CVE-2026-28348 · Red Hat security data · CC BY 4.0
This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences