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Fencer Vulns
medium 6.1

CVE-2026-28348 json

lxml_html_clean: CSS @import Filter Bypass via Unicode Escapes

published 2026-03-02 8 mo ago modified 2026-09-10 1 mo ago also EUVD-2026-9868 , GHSA-hw26-mmpg-fqfg , PYSEC-2026-2201

cvss
6.1
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.3%
EPSS 0.3% chance of exploitation in 30 days, percentile 20%
public exploits
0
none known

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.

Patch / fix

  • pypi lxml-html-clean 0.4.4
  • fedoralovespython lxml_html_clean 0.4.4
  • lxml Debian 12 4.9.2-1+deb12u1
  • lxml Debian 14, Debian 13 5.2.0-1
  • lxml-html-clean Debian 13 0.4.4-1~deb13u1
  • lxml-html-clean Debian 14 0.4.4-1

debian advisories DEBIAN-CVE-2026-28348

  • python-lxml_html_clean openSUSE Leap 16.0 0.4.2-bp160.2.1
  • python-lxml_html_clean openSUSE Tumbleweed 0.4.4-1.1

opensuse advisories openSUSE-SU-2026:20345-1openSUSE-SU-2026:10322-1

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2026-28348 updated cvss 6.1

lxml_html_clean: lxml_html_clean: Cross-Site Scripting (XSS) via CSS filter bypass

  • Red Hat All currently supported Red Hat products
    not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

CISA SSVC

Exploitation
Proof of concept is public
Automatable
no
Technical impact
partial
Assessed
8 mo ago

Exploit prediction

0.28% chance of exploitation in the next 30 days, higher than 20% of all scored CVEs (FIRST EPSS, 2026-11-08).

Exploits and checks

  • github.com https://github.com/fedora-python/lxml_html_clean/security/advisories/GHSA-hw26-mmpg-fqfg referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by version score vector
CNA 3.1 6.1 CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
GitHub 3.1 6.1 CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
OSV 3.1 6.1 CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N

Affected packages

ecosystem package affected fixed in
pypi lxml-html-clean
<0.4.4
0.4.4

Affected products

  • fedora-python lxml_html_clean

Classification

Weakness
  • CWE-116 Improper Encoding or Escaping of Output

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.

CPEs and fixed versions use Anchore's correction of NVD's data: Added CPE configurations because not yet analyzed by NVD.