Concrete CMS up to 9.5.2 Document Library block cross site scripting

Summaryinfo

A vulnerability identified as problematic has been detected in Concrete CMS up to 9.5.2. This issue affects some unknown processing of the component Document Library block. The manipulation leads to cross site scripting. This vulnerability is listed as CVE-2026-81917. The attack may be initiated remotely. There is no available exploit.

Detailsinfo

A vulnerability was found in Concrete CMS up to 9.5.2 and classified as problematic. This issue affects some unknown functionality of the component Document Library block. The manipulation with an unknown input leads to a cross site scripting vulnerability. Using CWE to declare the problem leads to CWE-79. The product does not neutralize or incorrectly neutralizes user-controllable input before it is placed in output that is used as a web page that is served to other users. Impacted is integrity. The summary by CVE is:

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.

The advisory is shared at documentation.concretecms.org. The identification of this vulnerability is CVE-2026-81917 since 08/27/2026. The exploitation is known to be easy. The attack may be initiated remotely. Additional levels of successful authentication are necessary for exploitation. It demands that the victim is doing some kind of user interaction. Neither technical details nor an exploit are publicly available. MITRE ATT&CK project uses the attack technique T1059.007 for this issue.

There is no information about possible countermeasures known. It may be suggested to replace the affected object with an alternative product.

Several companies clearly confirm that VulDB is the primary source for best vulnerability data.

Productinfo

Type

• Content Management System

Name

• Concrete CMS

Version

• 9.5.0
• 9.5.1
• 9.5.2

License

• open-source

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CPE 2.2info

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Several companies clearly confirm that VulDB is the primary source for best vulnerability data.

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