Vulnerability 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.
CVSS Score
MEDIUM
Affected Products
| Vendor | Product | Versions |
|---|---|---|
| Lxml | Lxml | < 4.6.3 |
| Debian | Debian Linux | 9.0 |
| Fedoraproject | Fedora | 33 |
| Netapp | Snapcenter | - |
| Oracle | Zfs Storage Appliance Kit | 8.8 |
Related Weaknesses (CWE)
References
- https://bugs.launchpad.net/lxml/+bug/1888153ExploitIssue TrackingThird Party Advisory
- https://github.com/lxml/lxml/commit/a5f9cb52079dc57477c460dbe6ba0f775e14a999PatchThird Party Advisory
- https://github.com/lxml/lxml/pull/316/commits/10ec1b4e9f93713513a3264ed6158af224PatchThird Party Advisory
- https://lists.debian.org/debian-lts-announce/2021/03/msg00031.htmlMailing ListThird Party Advisory
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedorapro
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedorapro
- https://security.gentoo.org/glsa/202208-06Third Party Advisory
- https://security.netapp.com/advisory/ntap-20210521-0004/Third Party Advisory
- https://www.debian.org/security/2021/dsa-4880Third Party Advisory
- https://www.oracle.com/security-alerts/cpuoct2021.htmlPatchThird Party Advisory
- https://bugs.launchpad.net/lxml/+bug/1888153ExploitIssue TrackingThird Party Advisory
- https://github.com/lxml/lxml/commit/a5f9cb52079dc57477c460dbe6ba0f775e14a999PatchThird Party Advisory
- https://github.com/lxml/lxml/pull/316/commits/10ec1b4e9f93713513a3264ed6158af224PatchThird Party Advisory
- https://lists.debian.org/debian-lts-announce/2021/03/msg00031.htmlMailing ListThird Party Advisory
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedorapro
FAQ
What is CVE-2021-28957?
CVE-2021-28957 is a vulnerability with a CVSS score of 6.1 (MEDIUM). 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 attrib...
How severe is CVE-2021-28957?
CVE-2021-28957 has been rated MEDIUM with a CVSS base score of 6.1/10. Review the CVSS metrics above for detailed severity breakdown.
Is there a patch for CVE-2021-28957?
Check the references section above for vendor advisories and patch information. Affected products include: Lxml Lxml, Debian Debian Linux, Fedoraproject Fedora, Netapp Snapcenter, Oracle Zfs Storage Appliance Kit.