---
id: CVE-2026-28350
aliases:
- GHSA-xvp8-3mhv-424c
- PYSEC-2026-2202
title: lxml-html-clean has tag injection through default Cleaner configuration
summary: lxml-html-clean has tag injection through default Cleaner configuration
severity: medium
cvss: 6.1
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N'
vendor: lxml-html-clean
product: lxml-html-clean
ecosystem: pip
affected:
- lxml-html-clean < 0.4.4
patched:
- lxml-html-clean 0.4.4
published: '2026-03-02'
updated: '2026-09-10'
sourceUpdated: '2026-09-10T03:50:41.927155700Z'
source: OSV
sourceUrl: 'https://osv.dev/vulnerability/GHSA-xvp8-3mhv-424c'
references:
- url: >-
https://github.com/fedora-python/lxml_html_clean/security/advisories/GHSA-xvp8-3mhv-424c
- url: 'https://nvd.nist.gov/vuln/detail/CVE-2026-28350'
- url: >-
https://github.com/fedora-python/lxml_html_clean/commit/9c5612ca33b941eec4178abf8a5294b103403f34
- url: 'https://github.com/fedora-python/lxml_html_clean'
tags:
- osv
- pip
epss: 0.00271
epssPercentile: 0.17426
ingestedAt: '2026-07-13T18:58:05.376Z'
---
## Overview
### Summary
The `` tag passes through the default `Cleaner` configuration. While `page_structure=True` removes `html`, `head`, and `title` tags, there is no specific handling for ``, allowing an attacker to inject it and hijack relative links on the page.
### Details
The `` tag is not currently in the `page_structure` kill set. Even though the specification says `` must be inside ``, browsers accept `` tags outside of the head.
If an attacker injects a `` tag, it changes the base URL for all relative URLs on the page (links, images, scripts) to a domain controlled by the attacker.
### PoC
```python
from lxml_html_clean import clean_html
# The base tag is preserved in the output
result = clean_html('Account')
print(result)
# Output:
```
### Impact
The injection of a `` tag allows an attacker to hijack the resolution of **all** relative URLs on the page. This results in three critical attack vectors:
1. **Phishing & Redirection:** Attackers can redirect user navigation (e.g., ``) and form submissions (e.g., `