CVE-2021-28957 Information

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 Vector

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

Reference

https://bugs.launchpad.net/lxml/+bug/1888153 https://github.com/lxml/lxml/pull/316/commits/10ec1b4e9f93713513a3264ed6158af22492f270 https://lists.debian.org/debian-lts-announce/2021/03/msg00031.html https://github.com/lxml/lxml/commit/a5f9cb52079dc57477c460dbe6ba0f775e14a999 https://www.debian.org/security/2021/dsa-4880 https://security.netapp.com/advisory/ntap-20210521-0004/ https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/3C2R44VDUY7FJVMAVRZ2WY7XYL4SVN45/ https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/XXN3QPWCTQVOGW4BMWV3AUUZZ4NRZNSQ/ https://www.oracle.com/security-alerts/cpuoct2021.html

Attack Complexity

LOW

Privileges Required

NONE

User Interaction Required

NONE

Scope

REQUIRED

Confidentiality Impact

CHANGED

Integrity Impact

LOW

Availability Impact

LOW

Base Score

NONE

Base Severity

6.1