CVE-2021-28957
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.
- Score
- CVSS 3.1 6.1 Medium
- Status
- Modified - cve@mitre.org
- Published
- 2021-03-21
- Last modified
- 2025-12-17
- Weaknesses
- CWE-79
Affected products
- Debian Linux (Debian)
- Fedora (Fedoraproject)
- Lxml (Lxml)
- Snapcenter (Netapp)
- Zfs Storage Appliance Kit (Oracle)
References
- https://bugs.launchpad.net/lxml/+bug/1888153
- https://github.com/lxml/lxml/commit/a5f9cb52079dc57477c460dbe6ba0f775e14a999
- https://github.com/lxml/lxml/pull/316/commits/10ec1b4e9f93713513a3264ed6158af22492f270
- https://lists.debian.org/debian-lts-announce/2021/03/msg00031.html
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/3C2R44VDUY7FJVMAVRZ2WY…
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/XXN3QPWCTQVOGW4BMWV3AU…
- https://security.gentoo.org/glsa/202208-06
- https://security.netapp.com/advisory/ntap-20210521-0004/
- https://www.debian.org/security/2021/dsa-4880
- https://www.oracle.com/security-alerts/cpuoct2021.html
