Vulnerability · Published Mar 5, 2026 · Assigned by GitHub_M
CVE-2026-28348lxml_html_clean: CSS @import Filter Bypass via Unicode Escapes
Medium 6.1
In plain English
A medium-severity security flaw in lxml_html_clean from fedora-python. Proof-of-concept exploit code is public. The chance it is exploited in the next 30 days is estimated at 0.3% (higher than 21% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.
Official description
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.
Affected packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| Debian:12 | lxml | 4.9.2-1+deb12u1 | DEBIAN-CVE-2026-28348 |
| Debian:13 | lxml | 5.2.0-1 | DEBIAN-CVE-2026-28348 |
| Debian:14 | lxml | 5.2.0-1 | DEBIAN-CVE-2026-28348 |
| Debian:13 | lxml-html-clean | 0.4.4-1~deb13u1 | DEBIAN-CVE-2026-28348 |
| Debian:14 | lxml-html-clean | 0.4.4-1 | DEBIAN-CVE-2026-28348 |
| PyPI | lxml-html-clean | 0.4.4 | GHSA-hw26-mmpg-fqfg |
| PyPI | lxml-html-clean | 0.4.4 | PYSEC-2026-2201 |
| Ubuntu:24.04:LTS | lxml-html-clean | no fix listed | UBUNTU-CVE-2026-28348 |
| Ubuntu:25.10 | lxml-html-clean | no fix listed | UBUNTU-CVE-2026-28348 |
| Ubuntu:26.04:LTS | lxml-html-clean | no fix listed | UBUNTU-CVE-2026-28348 |
| Ubuntu:26.10 | lxml-html-clean | no fix listed | UBUNTU-CVE-2026-28348 |
Affected products (as reported)
| Vendor | Product | Versions |
|---|---|---|
| fedora-python | lxml_html_clean | < 0.4.4 |
Weakness: CWE-116 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N