---
id: CVE-2026-81925
title: >-
  Concrete CMS before 9.5.3 improperly neutralized a user-supplied custom date
  format when rendering conversation messages, resulting in reflected cross-site
  scripting
summary: >-
  Concrete CMS before 9.5.3 improperly neutralized a user-supplied custom date
  format when rendering conversation messages, resulting in reflected cross-site
  scripting. An attacker could execute arbitrary JavaScript in the browser of a
  use…
severity: medium
cvss: 6.1
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N'
cwe:
  - CWE-79
vendor: concretecms
product: concrete_cms
affected:
  - concrete_cms < 9.5.3
patched:
  - concrete_cms 9.5.3
published: '2026-09-15'
updated: '2026-09-21'
sourceUpdated: '2026-09-21T17:53:13.887'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-81925'
references:
  - url: >-
      https://documentation.concretecms.org/developers/introduction/version-history/953-release-notes
    label: ff5b8ace-8b95-4078-9743-eac1ca5451de
tags:
  - nvd
  - cve.org
  - score-dispute
epss: 0.00414
epssPercentile: 0.35249
ssvc:
  exploitation: none
  automatable: 'no'
  technicalImpact: partial
  timestamp: '2026-09-16T17:46:17.138727Z'
scores:
  nvd: 6.1
  cna: 2.1
ingestedAt: '2026-09-15T20:44:02.417Z'
---

## Overview

Concrete CMS before 9.5.3 improperly neutralized a user-supplied custom date format when rendering conversation messages, resulting in reflected cross-site scripting. An attacker could execute arbitrary JavaScript in the browser of a user who was tricked into submitting a crafted POST request to the conversation view endpoint. Exploitation was aided by the absence of a CSRF token on the endpoint, which allowed the payload to be delivered through an auto-submitting cross-origin POST without authentication. The Concrete CMS security team gave this vulnerability a CVSS v4.0 score of 2.1 with vector CVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:P/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N. Thanks Yonatan Drori from Tenzai for reporting.

## Affected

- `concrete_cms < 9.5.3`

## Remediation

Upgrade past the affected range:

- `concrete_cms 9.5.3`