CVE-2021-32671

Flarum vulnerability

CVSS

10.0

EPSS

39.7%

EPSS pct

98th

Exploited

No known

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 <script>alert('test')</script> 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.

Affected vendor

Flarum

Affected product

Flarum

CVSS vector

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

Weakness type (CWE)

CWE-79 — Cross-Site Scripting (XSS)

Published

2021-06-07

Risk analysis

Based on its CVSS vector, this vulnerability is exploitable over the network, low attack complexity, requiring no privileges, no user interaction. Successful exploitation leads to high impact to confidentiality, high impact to integrity, high impact to availability.

Its EPSS score of 39.7% reflects a moderate probability of exploitation activity in the wild over the next 30 days, placing it above 98% of all scored CVEs.

Check your external exposure to CVE-2021-32671

Confirm whether Flarum Flarum is running on any internet-facing host or subdomain.
Match discovered service fingerprints against the version affected by CVE-2021-32671.
Prioritise remediation if the asset is public, business-critical, or near authentication/payment flows.

How ThreatPort helps with CVE-2021-32671

ThreatPort's external attack surface scanner checks your internet-facing assets — agentlessly, from the outside in — for the exposed services and versions that CVE-2021-32671 affects, then prioritises the finding by real risk using CISA KEV and FIRST.org EPSS.

Run a free external exposure scan

Are you exposed to CVE-2021-32671?

Run an instant, non-intrusive external scan to check your attack surface for CVE-2021-32671.

Start free scan

No credit card. Agentless.

Related vulnerabilities

CRITICAL

CVE-2017-8287

Freetype vulnerability

CRITICAL

CVE-2017-5135

Dpc3928sl Firmware vulnerability

CRITICAL

CVE-2017-7895

Linux Kernel vulnerability