Description
Concrete CMS before 9.5.3 contained a stored cross-site scripting vulnerability in SVG file handling. When SVG processing was set to the non-default "Reject files containing potentially harmful elements" mode (concrete.file_manager.images.svg_sanitization.action = reject), uploaded SVGs were checked only against a small built-in blocklist covering the script element and on* event-handler attributes; the broader enshrined/svg-sanitize pass still ran, but its result was discarded, so vectors it would have stripped, such as a javascript: URI in an xlink:href, were stored unmodified and executed when the file was opened directly. A user able to upload files could thereby run arbitrary JavaScript in the browser of any user who viewed the file. The default sanitize mode was not affected. The Concrete CMS security team gave this vulnerability a CVSS v4.0 score of 1.8 with vector CVSS:4.0/AV:N/AC:L/AT:P/PR:H/UI:A/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N. Thanks Oriol Ortiz for reporting.
Published: 2026-09-15
Score: 1.8 Low
EPSS: < 1% Very Low
KEV: No
Impact: n/a
Action: n/a
AI Analysis

No analysis available yet.

Remediation

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Tracking

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History

Wed, 16 Sep 2026 18:30:00 +0000

Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}


Wed, 16 Sep 2026 00:00:00 +0000

Type Values Removed Values Added
First Time appeared Concretecms
Concretecms concrete Cms
Vendors & Products Concretecms
Concretecms concrete Cms

Tue, 15 Sep 2026 20:30:00 +0000

Type Values Removed Values Added
Description Concrete CMS before 9.5.3 contained a stored cross-site scripting vulnerability in SVG file handling. When SVG processing was set to the non-default "Reject files containing potentially harmful elements" mode (concrete.file_manager.images.svg_sanitization.action = reject), uploaded SVGs were checked only against a small built-in blocklist covering the script element and on* event-handler attributes; the broader enshrined/svg-sanitize pass still ran, but its result was discarded, so vectors it would have stripped, such as a javascript: URI in an xlink:href, were stored unmodified and executed when the file was opened directly. A user able to upload files could thereby run arbitrary JavaScript in the browser of any user who viewed the file. The default sanitize mode was not affected. The Concrete CMS security team gave this vulnerability a CVSS v4.0 score of 1.8 with vector CVSS:4.0/AV:N/AC:L/AT:P/PR:H/UI:A/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N. Thanks Oriol Ortiz for reporting.
Title Concrete CMS before 9.5.3 is vulnerable to Stored XSS via SVG upload in "Reject" sanitization mode
Weaknesses CWE-79
References
Metrics cvssV4_0

{'score': 1.8, 'vector': 'CVSS:4.0/AV:N/AC:L/AT:P/PR:H/UI:A/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N'}


Subscriptions

Concretecms Concrete Cms
cve-icon MITRE

Status: PUBLISHED

Assigner: ConcreteCMS

Published:

Updated: 2026-09-16T17:52:45.158Z

Reserved: 2026-08-27T18:25:43.099Z

Link: CVE-2026-81927

cve-icon Vulnrichment

Updated: 2026-09-16T17:52:36.319Z

cve-icon NVD

Status : Awaiting Analysis

Published: 2026-09-15T21:16:43.220

Modified: 2026-09-16T19:16:15.097

Link: CVE-2026-81927

cve-icon Redhat

No data.

cve-icon OpenCVE Enrichment

Updated: 2026-09-15T23:45:17Z

Weaknesses
  • CWE-79

    Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')