CVE-2026-28348CWE-116

lxml_html_clean: CSS @import Filter Bypass via Unicode Escapes

Medium · published March 5, 2026

CVSS v3.1
6.1
EPSS
0%
Percentile
21.2
In the wild
Unconfirmed
What it is

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.

The record
Technical detail
CVSS v3.1
6.1 · MEDIUM
Vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
CVSS v4.0
Not supplied
EPSS
0.00297 · 21.2th percentile
Weakness
CWE-116 · Improper Encoding or Escaping of Output
Published
2026-03-05T19:49Z
EPSS history
Timeline
  • 05 MAR 19:49Z
    lxml_html_clean: CSS @import Filter Bypass via Unicode Escapes
    cvelistv5