CVE-2021-28957

    Dashboard / Vulnerabilities / CVE-2021-28957

    CVE-2021-28957

    Published: 21 Mar 2021Last Modified: 8 Jul 2026

    Summary:

    Details: 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://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/3C2R44VDUY7FJVMAVRZ2WY7XYL4SVN45/, https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/XXN3QPWCTQVOGW4BMWV3AUUZZ4NRZNSQ/, https://lists.debian.org/debian-lts-announce/2021/03/msg00031.html, https://security.gentoo.org/glsa/202208-06, https://security.netapp.com/advisory/ntap-20210521-0004/, https://www.debian.org/security/2021/dsa-4880, https://bugs.launchpad.net/lxml/+bug/1888153, https://github.com/lxml/lxml/commit/a5f9cb52079dc57477c460dbe6ba0f775e14a999, https://github.com/lxml/lxml/pull/316/commits/10ec1b4e9f93713513a3264ed6158af22492f270, https://www.oracle.com/security-alerts/cpuoct2021.html

    Affected packages

    Package

    Name:

    Purl:

    Affected ranges

    Type: GIT

    Events:

    Introduced- 0
    Fixed -a5f9cb52079dc57477c460dbe6ba0f775e14a999

    Affected versions

    lxml-4.6.2
    lxml-4.6.1
    lxml-4.6.0

    Common Vulnerability Scoring System

    Attack Vector
    Network
    Adjacent
    Local
    Physical
    Privileges Required
    None
    Low
    High
    User Interaction
    None
    Required
    Scope
    Unchanged
    Changed
    Confidentiality
    None
    Low
    High
    Integrity
    None
    Low
    High
    Availability
    None
    Low
    High
    CVE-2021-28957 | CVE-DB