// For flags

CVE-2021-28957

python-lxml: Missing input sanitization for formaction HTML5 attributes may lead to XSS

Severity Score

6.1
*CVSS v3.1

Exploit Likelihood

*EPSS

Affected Versions

*CPE

Public Exploits

1
*Multiple Sources

Exploited in Wild

-
*KEV

Decision

-
*SSVC
Descriptions

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.

Se ha descubierto una vulnerabilidad XSS en las versiones del módulo clean de python-lxml anteriores a la versión 4.6.3. Al desactivar los argumentos safe_attrs_only y forms, la clase Cleaner no elimina el atributo formaction, lo que permite que JS eluda el sanitizador. Un atacante remoto podría aprovechar este fallo para ejecutar código JS arbitrario en usuarios que interactúen con HTML incorrectamente saneado. Este problema está parcheado en lxml versión 4.6.3

A flaw was found in python-lxml. The HTML5 formaction attribute is not input sanitized like the HTML action attribute is which can lead to a Cross-Site Scripting attack (XSS) when an application uses python-lxml to sanitize user inputs. The highest threat from this vulnerability is to data confidentiality and integrity as well as system availability.

*Credits: N/A
CVSS Scores
Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
Required
Scope
Changed
Confidentiality
Low
Integrity
Low
Availability
None
Attack Vector
Network
Attack Complexity
Medium
Authentication
None
Confidentiality
None
Integrity
Partial
Availability
None
* Common Vulnerability Scoring System
SSVC
  • Decision:-
Exploitation
-
Automatable
-
Tech. Impact
-
* Organization's Worst-case Scenario
Timeline
  • 2021-03-21 CVE Reserved
  • 2021-03-21 CVE Published
  • 2023-11-08 EPSS Updated
  • 2024-08-03 CVE Updated
  • 2024-08-03 First Exploit
  • ---------- Exploited in Wild
  • ---------- KEV Due Date
CWE
  • CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
CAPEC
Affected Vendors, Products, and Versions
Vendor Product Version Other Status
Vendor Product Version Other Status <-- --> Vendor Product Version Other Status
Lxml
Search vendor "Lxml"
 Lxml
Search vendor "Lxml" for product "Lxml"
 < 4.6.3
Search vendor "Lxml" for product "Lxml" and version " < 4.6.3"
-
Affected
Debian
Search vendor "Debian"
 Debian Linux
Search vendor "Debian" for product "Debian Linux"
 9.0
Search vendor "Debian" for product "Debian Linux" and version "9.0"
-
Affected
Debian
Search vendor "Debian"
 Debian Linux
Search vendor "Debian" for product "Debian Linux"
 10.0
Search vendor "Debian" for product "Debian Linux" and version "10.0"
-
Affected
Fedoraproject
Search vendor "Fedoraproject"
 Fedora
Search vendor "Fedoraproject" for product "Fedora"
 33
Search vendor "Fedoraproject" for product "Fedora" and version "33"
-
Affected
Fedoraproject
Search vendor "Fedoraproject"
 Fedora
Search vendor "Fedoraproject" for product "Fedora"
 34
Search vendor "Fedoraproject" for product "Fedora" and version "34"
-
Affected
Netapp
Search vendor "Netapp"
 Snapcenter
Search vendor "Netapp" for product "Snapcenter"
--
Affected
Oracle
Search vendor "Oracle"
 Zfs Storage Appliance Kit
Search vendor "Oracle" for product "Zfs Storage Appliance Kit"
 8.8
Search vendor "Oracle" for product "Zfs Storage Appliance Kit" and version "8.8"
-
Affected