CVE-2021-28957
6.1 · MEDIUMAn XSS vulnerability was discovered in python-lxml's clean module versions before 4.6.3.
Overview
CVE-2021-28957 is a medium-severity vulnerability. It was published on March 21, 2021 and has a CVSS 3.1 base score of 6.1 (MEDIUM).
This vulnerability has a CVSS 3.1 base score of 6.1, rated MEDIUM. It can be exploited remotely over the network. No authentication or special privileges are required for exploitation.
Technical 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.
Remediation
Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.
References
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Frequently asked questions
What is CVE-2021-28957?
CVE-2021-28957 is a medium-severity vulnerability. It was published on March 21, 2021 and has a CVSS 3.1 base score of 6.1 (MEDIUM).
How severe is CVE-2021-28957?
This vulnerability has a CVSS 3.1 base score of 6.1, rated MEDIUM. It can be exploited remotely over the network. No authentication or special privileges are required for exploitation.
How do I fix or remediate CVE-2021-28957?
Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.
How can CyberStrike help with CVE-2021-28957?
CyberStrike is an open-source, AI-augmented pentesting engine. Rather than flag a version number, it tests whether an issue like CVE-2021-28957 is actually reachable in your own applications and APIs, then verifies each finding before reporting it. That tells you if the weakness is a real, exploitable risk in your environment or a false positive you can safely deprioritize.
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