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CVE-2026-81917

5.4 · MEDIUM

Concrete CMS below 9.5.3 does not apply HTML output escaping to the file description and tags fields when rendering the Document Library block, so a user with permission to edit file properties cou…

Published Sep 11, 2026concretecmsCWE-79EPSS 0.24%

Overview

CVE-2026-81917 is a medium-severity vulnerability affecting concretecms concrete_cms. It was published on September 11, 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 below 9.5.3 does not apply HTML output escaping to the file description and tags fields when rendering the Document Library block, so a user with permission to edit file properties could store a script payload that executed in the browser of any visitor to a page displaying the block with the description or tags column enabled, including unauthenticated visitors. Successful exploitation could allow theft of session data or actions performed in the visitor's context. The block controller returned the description and tags values without the h() escaping already applied to the title column, and the block view template wrote the returned value directly into the results table The Concrete CMS security team gave this vulnerability a CVSS v4.0 score of 5.1 with vector CVSS:4.0/AV:N/AC:L/AT:P/PR:H/UI:N/VC:L/VI:L/VA:N/SC:H/SI:H/SA:N. Thanks Nguyen Manh Thuan 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-2026-81917?

CVE-2026-81917 is a medium-severity vulnerability affecting concretecms concrete_cms. It was published on September 11, 2026 and has a CVSS 3.1 base score of 5.4 (MEDIUM).

How severe is CVE-2026-81917?

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-2026-81917?

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-2026-81917?

CyberStrike is an open-source, AI-augmented pentesting engine. Rather than flag a version number, it tests whether an issue like CVE-2026-81917 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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