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CVE-2026-81894

5.4 · MEDIUM

Concrete CMS 9.5.2 and below is vulnerable to stored DOM-based Cross-site Scripting (XSS) via the Gallery block's per-image Caption field because the bundled Magnific Popup lightbox script (concret…

Published Sep 15, 2026concretecmsCWE-89EPSS 0.24%

Overview

CVE-2026-81894 is a medium-severity vulnerability affecting concretecms concrete_cms. It was published on September 15, 2026 and has a CVSS 3.1 base score of 5.4 (MEDIUM).

This vulnerability has a CVSS 3.1 base score of 5.4, rated MEDIUM. It can be exploited remotely over the network. Some level of privileges is required for exploitation.

Technical description

Concrete CMS 9.5.2 and below is vulnerable to stored DOM-based Cross-site Scripting (XSS) via the Gallery block's per-image Caption field because the bundled Magnific Popup lightbox script (concrete/js/features/imagery/frontend.js) re-parses the attribute-decoded caption as HTML through jQuery's .append() in titleSrc instead of inserting it as text. A user with permission to edit a page containing a Gallery block can store a caption that executes in the browser of any visitor who opens that image's lightbox. The Concrete CMS security team gave this vulnerability a CVSS v.4.0 score of 8.5 with vector CVSS:4.0/AV:N/AC:L/AT:N/PR:H/UI:P/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N. Thanks Yonatan Drori (Tenzai) for reporting.

Remediation

Check the references section for vendor advisories and patches from concretecms. Update concrete_cms to the latest patched version. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

Affected products

VendorProductVersionsStatus
concretecmsconcrete_cms>= 0, < 9.5.3Affected

References

Refdocumentation.concretecms.org/developers/introduction/version-history/953-release-notes

How CyberStrike helps

Frequently asked questions

What is CVE-2026-81894?

CVE-2026-81894 is a medium-severity vulnerability affecting concretecms concrete_cms. It was published on September 15, 2026 and has a CVSS 3.1 base score of 5.4 (MEDIUM).

How severe is CVE-2026-81894?

This vulnerability has a CVSS 3.1 base score of 5.4, rated MEDIUM. It can be exploited remotely over the network. Some level of privileges is required for exploitation.

How do I fix or remediate CVE-2026-81894?

Check the references section for vendor advisories and patches from concretecms. Update concrete_cms to the latest patched version. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

How can CyberStrike help with CVE-2026-81894?

CyberStrike is an open-source, AI-augmented pentesting engine. Rather than flag a version number, it tests whether an issue like CVE-2026-81894 is actually reachable in your own applications and APIs, then verifies each finding before reporting it. That tells you if the weakness is a real, exploitable risk in your environment or a false positive you can safely deprioritize.

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