An attacker can inject a <base> element into HTML processed by lxml_html_clean because the default Cleaner configuration does not remove it. Once in place, all relative URLs in the page resolve to the attacker‑supplied base, allowing malicious links or redirects. The flaw is identified as CWE‑116 and results in a moderate risk of phishing or compromised navigation for users.

fedora-python’s lxml_html_clean package is impacted. Versions prior to 0.4.4, including the default configuration used by applications relying on the library, are vulnerable. The issue is resolved in 0.4.4 and later.

The CVSS score of 6.1 indicates a medium‑to‑high severity. The EPSS score of less than 1 % suggests that exploitation is unlikely but not impossible. The vulnerability is not listed in the CISA KEV catalog, and no commercial exploit is known. Attackers could exploit the flaw by submitting malicious HTML content to any application that imports lxml_html_clean with the default Cleaner settings, thereby hijacking relative links.