GHSA-xvp8-3mhv-424c
Suggest an improvement- Source
- https://github.com/advisories/GHSA-xvp8-3mhv-424c
- Import Source
- https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/03/GHSA-xvp8-3mhv-424c/GHSA-xvp8-3mhv-424c.json
- JSON Data
- https://api.osv.dev/v1/vulns/GHSA-xvp8-3mhv-424c
- Aliases
- Related
- Published
- 2026-03-02T19:35:52Z
- Modified
- 2026-03-10T18:44:00.312921Z
- Severity
-
- 6.1 (Medium) CVSS_V3 - CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N CVSS Calculator
- Summary
- lxml-html-clean has <base> tag injection through default Cleaner configuration
- Details
-
Summary
The
<base>tag passes through the defaultCleanerconfiguration. Whilepage_structure=Trueremoveshtml,head, andtitletags, there is no specific handling for<base>, allowing an attacker to inject it and hijack relative links on the page.Details
The
<base>tag is not currently in thepage_structurekill set. Even though the specification says<base>must be inside<head>, browsers accept<base>tags outside of the head.If an attacker injects a
<base>tag, it changes the base URL for all relative URLs on the page (links, images, scripts) to a domain controlled by the attacker.PoC
from lxml_html_clean import clean_html # The base tag is preserved in the output result = clean_html('<base href="http://evil.com/"><a href="/account">Account</a>') print(result) # Output: <div><base href="http://evil.com/">...<a href="/account">Account</a></div>Impact
The injection of a
<base>tag allows an attacker to hijack the resolution of all relative URLs on the page. This results in three critical attack vectors:- Phishing & Redirection: Attackers can redirect user navigation (e.g.,
<a href="/login">) and form submissions (e.g.,<form action="/auth">) to an attacker-controlled domain, effectively stealing credentials or sensitive data without the user realizing they have left the legitimate site. - Cross-Site Scripting (XSS): If the victim application loads JavaScript files using relative paths (e.g.,
<script src="assets/app.js">), the browser will attempt to fetch the script from the attacker's domain. This upgrades the vulnerability from HTML injection to full Stored XSS. - Defacement: Relative references to images (
<img>) and stylesheets (<link>) will be loaded from the attacker's server, allowing for UI redressing or defacement.
- Phishing & Redirection: Attackers can redirect user navigation (e.g.,
- Database specific
{ "github_reviewed": true, "github_reviewed_at": "2026-03-02T19:35:52Z", "severity": "MODERATE", "nvd_published_at": "2026-03-05T20:16:16Z", "cwe_ids": [ "CWE-116" ] }- References
Affected packages
PyPI / lxml-html-clean
Package
- Name
- lxml-html-clean
- View open source insights on deps.dev
- Purl
- pkg:pypi/lxml-html-clean