Vulnerability Details CVE-2026-81901
In Concrete CMS 9.2.0 through 9.5.2, the REST API page update endpoint (PUT /ccm/api/1.0/pages/{cID}) did not enforce page-property, page-template, or page-type authorization. A user granted only content-editing rights on a page could therefore alter its properties, template, and type through the API, and could set the header_extra_content attribute, which is rendered unescaped into the head element of every page, to persist JavaScript that executed in the browser of every visitor, including higher-privileged reviewers who approve the page version. The Concrete CMS security team gave this vulnerability a CVSS v4.0 score of 7.2 with vector CVSS:4.0/AV:N/AC:L/AT:P/PR:H/UI:P/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N. Thanks Yonatan Drori from Tenzai for reporting.
Exploit prediction scoring system (EPSS) score
EPSS Score 0.003
EPSS Ranking 17.8%
CVSS Severity
CVSS v3 Score 8.7
References
Products affected by CVE-2026-81901
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cpe:2.3:a:concretecms:concrete_cms:9.2.0
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cpe:2.3:a:concretecms:concrete_cms:9.2.1
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cpe:2.3:a:concretecms:concrete_cms:9.2.2
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cpe:2.3:a:concretecms:concrete_cms:9.2.3
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cpe:2.3:a:concretecms:concrete_cms:9.2.4
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cpe:2.3:a:concretecms:concrete_cms:9.2.5
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cpe:2.3:a:concretecms:concrete_cms:9.2.6
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cpe:2.3:a:concretecms:concrete_cms:9.2.7
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cpe:2.3:a:concretecms:concrete_cms:9.2.8
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cpe:2.3:a:concretecms:concrete_cms:9.2.9
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cpe:2.3:a:concretecms:concrete_cms:9.3.0
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cpe:2.3:a:concretecms:concrete_cms:9.3.1
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cpe:2.3:a:concretecms:concrete_cms:9.3.2
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cpe:2.3:a:concretecms:concrete_cms:9.3.3
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cpe:2.3:a:concretecms:concrete_cms:9.3.4
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cpe:2.3:a:concretecms:concrete_cms:9.3.5
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cpe:2.3:a:concretecms:concrete_cms:9.3.6
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cpe:2.3:a:concretecms:concrete_cms:9.3.7
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cpe:2.3:a:concretecms:concrete_cms:9.3.8
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cpe:2.3:a:concretecms:concrete_cms:9.3.9
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cpe:2.3:a:concretecms:concrete_cms:9.4.0
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cpe:2.3:a:concretecms:concrete_cms:9.4.1
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cpe:2.3:a:concretecms:concrete_cms:9.4.2
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cpe:2.3:a:concretecms:concrete_cms:9.4.3
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cpe:2.3:a:concretecms:concrete_cms:9.4.4
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cpe:2.3:a:concretecms:concrete_cms:9.4.5
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cpe:2.3:a:concretecms:concrete_cms:9.4.6
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cpe:2.3:a:concretecms:concrete_cms:9.4.7
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cpe:2.3:a:concretecms:concrete_cms:9.4.8
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cpe:2.3:a:concretecms:concrete_cms:9.5.0
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cpe:2.3:a:concretecms:concrete_cms:9.5.1
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cpe:2.3:a:concretecms:concrete_cms:9.5.2