CVE-2021-32671 Information

Description

Flarum is a forum software for building communities. Flarum’s translation system allowed for string inputs to be converted into HTML DOM nodes when rendered. This change was made after v0.1.0-beta.16 (our last beta before v1.0.0) and was not noticed or documented. This allowed for any user to type malicious HTML markup within certain user input fields and have this execute on client browsers. The example which led to the discovery of this vulnerability was in the forum search box. Entering faux-malicious HTML markup such as resulted in an alert box appearing on the forum. This attack could also be modified to perform AJAX requests on behalf of a user possibly deleting discussions modifying their settings or profile or even modifying settings on the Admin panel if the attack was targetted towards a privileged user. All Flarum communities that run flarum v1.0.0 or v1.0.1 are impacted. The vulnerability has been fixed and published as flarum/core v1.0.2. All communities running Flarum v1.0 have to upgrade as soon as possible to v1.0.2.

CVSS Vector

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

Reference

https://packagist.org/packages/flarum/core https://github.com/flarum/core/security/advisories/GHSA-5qjq-69w6-fg57 https://github.com/flarum/core/commit/440bed81b8019dff00642c8f493b4909d505a28a

Attack Complexity

LOW

Privileges Required

NONE

User Interaction Required

NONE

Scope

NONE

Confidentiality Impact

CHANGED

Integrity Impact

HIGH

Availability Impact

HIGH

Base Score

HIGH

Base Severity

10.0