CVE-2021-28957

MediumCVSS 6.1/10Last modified Jun 17, 2026

Description

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.

Metrics

CVSS 3.1 6.1/10CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N

Weakness enumeration

CWE-79

Affected software

VendorProductVersions
n/an/an/a

References

Timeline

Published
Mar 21, 2021
Last modified
Jun 17, 2026
NVD status
Modified

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CVE-2021-28957: Medium severity, CVSS 6.1 | Vulnix