Python
CVE-2021-28957
MEDIUM
Severity by source
AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
Primary rating from NVD · only source for this CVE.
CVSS VectorNVD
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
Lifecycle Timeline
1Blast Radius
ecosystem impact- 146 pypi packages depend on lxml (141 direct, 5 indirect)
Ecosystem-wide dependent count for version 4.6.3.
DescriptionNVD
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.
AnalysisAI
An XSS vulnerability was discovered in python-lxml's clean module versions before 4.6.3. Rated medium severity (CVSS 6.1), this vulnerability is remotely exploitable, no authentication required, low attack complexity. Public exploit code available.
Technical ContextAI
This vulnerability is classified as Cross-Site Scripting (XSS) (CWE-79), which allows attackers to inject malicious scripts into web pages viewed by other users. 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. Affected products include: Lxml, Debian Debian Linux, Fedoraproject Fedora, Netapp Snapcenter, Oracle Zfs Storage Appliance Kit. Version information: before 4.6.3..
RemediationAI
A vendor patch is available. Apply the latest security update as soon as possible. Sanitize all user input, use Content-Security-Policy headers, encode output contextually (HTML, JS, URL). Use frameworks with built-in XSS protection.
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External POC / Exploit Code
Leaving vuln.today