CVE-2026-28348 lxml_html_clean: CSS @import Filter Bypass via Unicode Escapes
Attackers can bypass CSS filters using Unicode escapes to inject malicious scripts, leading to XSS in older browsers.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- A user has to click or open something
- Fix
- Available
What is CVE-2026-28348?
CVE-2026-28348 is a medium-severity cross-site scripting vulnerability in fedora-python lxml_html_clean, published on 5 Mar 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.
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.
Weakness: CWE-116
Which versions are affected by CVE-2026-28348?
3 open source packages ship an affected version, including lxml-html-clean. It affects 1 product.
| Package | Affected | Fixed in |
|---|---|---|
lxml-html-clean PyPI | All versions | 0.4.4 |
lxml-html-clean PyPI | All versions | 0.4.4 |
lxml-html-clean PyPI | All versions | 0.4.4 |
Products include Fedoralovespython Lxml Html Clean.
How do I fix CVE-2026-28348?
Upgrade lxml-html-clean to 0.4.4 or later.
Escape output for the context it lands in and set a strict Content Security Policy. Upgrading the affected component is the real fix. More about Cross-site scripting.
Is CVE-2026-28348 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-28348 exists.
Other vulnerabilities in fedora-python lxml_html_clean
Sources
Also known as DEBIAN-CVE-2026-28348, GHSA-hw26-mmpg-fqfg, MINI-qr5v-rg5q-mqwq, PYSEC-2026-2201, UBUNTU-CVE-2026-28348.