CVE-2021-41252 Cross-site scripting (XSS) from writer field content in the site frontend

2021-11-1618:05:10

CWE-79

GitHub_M

www.cve.org

cve-2021-41252

cross-site scripting

xss

kirby

html code

api

sanitizing

vulnerability

patched

CVSS3

7.3

Attack Vector

NETWORK

Attack Complexity

LOW

Privileges Required

LOW

User Interaction

REQUIRED

Scope

UNCHANGED

Confidentiality Impact

HIGH

Integrity Impact

HIGH

Availability Impact

NONE

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

EPSS

0.001

Percentile

25.8%

JSON

Kirby is an open source file structured CMS ### Impact Kirby’s writer field stores its formatted content as HTML code. Unlike with other field types, it is not possible to escape HTML special characters against cross-site scripting (XSS) attacks, otherwise the formatting would be lost. If the user is logged in to the Panel, a harmful script can for example trigger requests to Kirby’s API with the permissions of the victim. Because the writer field did not securely sanitize its contents on save, it was possible to inject malicious HTML code into the content file by sending it to Kirby’s API directly without using the Panel. This malicious HTML code would then be displayed on the site frontend and executed in the browsers of site visitors and logged in users who are browsing the site. Attackers must be in your group of authenticated Panel users in order to exploit this weakness. Users who do not make use of the writer field are not affected. This issue has been patched in Kirby 3.5.8 by sanitizing all writer field contents on the backend whenever the content is modified via Kirby’s API. Please update to this or a later version to fix the vulnerability.

CNA Affected

[
  {
    "product": "kirby",
    "vendor": "getkirby",
    "versions": [
      {
        "status": "affected",
        "version": ">= 3.5.0, < 3.5.8"
      }
    ]
  }
]