CVE-2021-28957

critical

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.

References

https://www.oracle.com/security-alerts/cpuoct2021.html

https://www.debian.org/security/2021/dsa-4880

https://security.netapp.com/advisory/ntap-20210521-0004/

https://security.gentoo.org/glsa/202208-06

https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/XXN3QPWCTQVOGW4BMWV3AUUZZ4NRZNSQ/

https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/3C2R44VDUY7FJVMAVRZ2WY7XYL4SVN45/

https://lists.debian.org/debian-lts-announce/2021/03/msg00031.html

https://github.com/lxml/lxml/pull/316/commits/10ec1b4e9f93713513a3264ed6158af22492f270

https://github.com/lxml/lxml/commit/a5f9cb52079dc57477c460dbe6ba0f775e14a999

https://bugs.launchpad.net/lxml/+bug/1888153

Details

Source: Mitre, NVD

Published: 2021-03-21

Updated: 2024-11-21

Risk Information

CVSS v2

Base Score: 4.3

Vector: CVSS2#AV:N/AC:M/Au:N/C:N/I:P/A:N

Severity: Medium

CVSS v3

Base Score: 6.1

Vector: CVSS:3.0/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N

Severity: Medium

CVSS v4

Base Score: 9.3

Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N

Severity: Critical