Concrete CMS before 9.5.3 improperly neutralized a user-supplied custom date format when rendering conversation messages, resulting in reflected cross-site scripting. An attacker could execute arbitrary JavaScript in the browser of a user who was tricked into submitting a crafted POST request to the conversation view endpoint. Exploitation was aided by the absence of a CSRF token on the endpoint, which allowed the payload to be delivered through an auto-submitting cross-origin POST without authentication. The Concrete CMS security team gave this vulnerability a CVSS v4.0 score of 2.1 with vector CVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:P/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N. Thanks Yonatan Drori from Tenzai for reporting.

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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 00:15:00 +0000

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

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

Type Values Removed Values Added
Description Concrete CMS before 9.5.3 improperly neutralized a user-supplied custom date format when rendering conversation messages, resulting in reflected cross-site scripting. An attacker could execute arbitrary JavaScript in the browser of a user who was tricked into submitting a crafted POST request to the conversation view endpoint. Exploitation was aided by the absence of a CSRF token on the endpoint, which allowed the payload to be delivered through an auto-submitting cross-origin POST without authentication. The Concrete CMS security team gave this vulnerability a CVSS v4.0 score of 2.1 with vector CVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:P/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N. Thanks Yonatan Drori from Tenzai for reporting.
Title Concrete CMS below 9.5.3 is vulnerable to Reflected Cross-Site Scripting (XSS) via Conversation Custom Date Format
Weaknesses CWE-79
References
Metrics cvssV4_0

{'score': 2.1, 'vector': 'CVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:P/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N'}


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cve-icon MITRE

Status: PUBLISHED

Assigner: ConcreteCMS

Published:

Updated: 2026-09-16T17:48:00.821Z

Reserved: 2026-08-27T18:25:17.660Z

Link: CVE-2026-81925

cve-icon Vulnrichment

Updated: 2026-09-16T17:47:55.929Z

cve-icon NVD

Status : Awaiting Analysis

Published: 2026-09-15T20:18:04.090

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

Link: CVE-2026-81925

cve-icon Redhat

No data.

cve-icon OpenCVE Enrichment

Updated: 2026-09-16T19:00:10Z

Weaknesses