No exploitation reportedFix available

CVE-2021-32671

No exploitation reported by the sources we read.

Published2021-06-07
WeaknessCWE-79

Am I affected?

With a domain, we read the version its public headers and pages expose. A distribution build can carry the fix under an older number.

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 <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.

Timeline

dates in UTC

2021-06-0722:15CVE publishedNVD
2026-10-2319:23EPSS crossed 10 %FIRST EPSS

Observed activity

isMalicious corpus · updated 2026-10-23 18:48 UTC

Indicators tagged with this CVE, per day0 indicators over 7 days

Block these indicators

Firewall list (EDL, text): https://api.ismalicious.com/edl/cve/CVE-2021-32671?format=txt
CSV export: https://api.ismalicious.com/edl/cve/CVE-2021-32671?format=csv
TAXII collection of exploited CVEs
The EDL and CSV take an API key on the Pro plan.

Versions per branch

NVD

Flarum

Branch	Affected	Fixed in	Source
1.0	= 1.0.0	no fix published	NVD
1.0	= 1.0.1	no fix published	NVD

as publishedRanges as NVD and OSV publish them; a distribution’s build can be fixed under an older number.

Fix

Advisories and patches

github.comPatch

Detection

Nuclei template: none so far
Exploit-DB: no entry
Proof-of-concept repositories: none listed

Sources

CNACVSS 3.110read 2026-10-23
NVDCVSS 3.110read 2026-10-23
NVDCVSS 2.04.3read 2026-10-23
CNAweakness (CWE)CWE-79read 2026-10-23
FIRST EPSSEPSS score39.7 %read 2026-10-23

Technical details

CVSS v3 Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H
Published: 2021-06-07
Last Modified: 2026-06-17
NVD status: Modified

Frequently asked questions

What is CVE-2021-32671?

Is CVE-2021-32671 actively exploited?

Active exploitation of CVE-2021-32671 has not been confirmed. Its EPSS score was 39.7% on 2026-10-22, the estimated probability of exploitation in the next 30 days.

What is the CVSS score for CVE-2021-32671?

CVE-2021-32671 has a CVSS v3 base score of 10 (CRITICAL severity), with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H.

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