---
id: CVE-2026-81903
title: >-
  Concrete CMS versions 9.0.0 to 9.5.2 stored the Page Container icon value
  submitted through the dashboard without validating it against the set of known
  container icons
summary: >-
  Concrete CMS versions 9.0.0 to 9.5.2 stored the Page Container icon value
  submitted through the dashboard without validating it against the set of known
  container icons. The unvalidated value was later concatenated into the src
  attribute…
severity: medium
cvss: 5.4
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N'
cwe:
  - CWE-79
vendor: concretecms
product: concrete_cms
affected:
  - 'concrete_cms >= 9.0.0, < 9.5.3'
patched:
  - concrete_cms 9.5.3
published: '2026-09-14'
updated: '2026-09-18'
sourceUpdated: '2026-09-18T19:12:09.993'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-81903'
references:
  - url: >-
      https://documentation.concretecms.org/developers/introduction/version-history/953-release-notes
    label: ff5b8ace-8b95-4078-9743-eac1ca5451de
tags:
  - nvd
  - cve.org
epss: 0.00322
epssPercentile: 0.22557
ssvc:
  exploitation: none
  automatable: 'no'
  technicalImpact: total
  timestamp: '2026-09-15T14:45:40.318011Z'
scores:
  nvd: 5.4
  cna: 7
ingestedAt: '2026-09-14T21:15:17.564Z'
---

## Overview

Concrete CMS versions 9.0.0 to 9.5.2 stored the Page Container icon value submitted through the dashboard without validating it against the set of known container icons. The unvalidated value was later concatenated into the src attribute of an img tag by a helper that did not encode attribute output, and was rendered raw in the Containers dashboard list and editor views. A user with delegated access to the Page Containers dashboard could store a crafted icon value that broke out of the src attribute and executed script in the authenticated session of another editor or administrator who viewed the list, enabling session token theft and privileged dashboard actions. The Concrete CMS security team gave this vulnerability a CVSS v4.0 score of 7.0 with vector CVSS:4.0/AV:A/AC:L/AT:N/PR:H/UI:P/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N. Thanks Andrew Gonzalez for reporting.

## Affected

- `concrete_cms >= 9.0.0, < 9.5.3`

## Remediation

Upgrade past the affected range:

- `concrete_cms 9.5.3`