CVE-2026-28350 lxml_html_clean: <base> tag injection through default Cleaner configuration

Medium 6.1 Published 5 Mar 2026 Updated 6 Mar 2026

Attackers can inject base tags to hijack relative links in HTML content processed by the default configuration of this Python library.

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-2026-28350?

CVE-2026-28350 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 <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.

Weakness: CWE-116

Which versions are affected by CVE-2026-28350?

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-2026-28350?

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-2026-28350 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-28350 exists.

Sources

Also known as DEBIAN-CVE-2026-28350, GHSA-xvp8-3mhv-424c, MINI-j77g-phqp-cv3x, PYSEC-2026-2202, UBUNTU-CVE-2026-28350.