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Fencer Vulns
medium 6.1

CVE-2026-28350 json

lxml_html_clean: <base> tag injection through default Cleaner configuration

published 2026-03-02 8 mo ago modified 2026-09-10 1 mo ago also EUVD-2026-20098 , GHSA-xvp8-3mhv-424c , PYSEC-2026-2202

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 22%
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 <base> tag passes through the default Cleaner configuration. While page_structure=True removes html, head, and title tags, there is no specific handling for <base>, allowing an attacker to inject it and hijack relative links on the page. 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-2026-28350

  • 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-2026-28350 updated cvss 6.1

lxml_html_clean: lxml_html_clean: Web link hijacking due to improper base tag handling

  • 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

0.30% chance of exploitation in the next 30 days, higher than 22% 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-xvp8-3mhv-424c 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.