An XSS vulnerability was discovered in python-lxml's clean module versions before 4.6.3. When disabling the safe_attrs_only and forms arguments, the Cleaner class does not remove the formaction attribute allowing for JS to bypass the sanitizer. A remote attacker could exploit this flaw to run arbitrary JS code on users who interact with incorrectly sanitized HTML. This issue is patched in lxml 4.6.3.
History

Wed, 17 Dec 2025 22:15:00 +0000

Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}


cve-icon MITRE

Status: PUBLISHED

Assigner: mitre

Published:

Updated: 2025-12-17T21:31:43.446Z

Reserved: 2021-03-21T00:00:00.000Z

Link: CVE-2021-28957

cve-icon Vulnrichment

Updated: 2024-08-03T21:55:12.376Z

cve-icon NVD

Status : Modified

Published: 2021-03-21T05:15:13.367

Modified: 2025-12-17T22:15:56.740

Link: CVE-2021-28957

cve-icon Redhat

Severity : Moderate

Publid Date: 2021-03-21T00:00:00Z

Links: CVE-2021-28957 - Bugzilla

cve-icon OpenCVE Enrichment

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