CVE-2026-81901 — Concrete CMS 9.2.0 to 9.5.2 is vulnerable to stored XSS due to missing authorization in the `PUT /pages/{cID}` endpoint

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.

Published Sep 14, 2026Updated Sep 14, 2026Sources: cvelistV5, ConcreteCMS

Triage

Is it exploited, how likely is exploitation, what does it touch, and how severe do the scoring sources call it.

Exploitation

Unreported

no source claims exploitation

EPSS

Not scored

FIRST has not published a score

Affects

concrete cms

concrete_cms

CVSS base

7.2

HIGH

Affected scope

The catalog records vendors and products as separate lists, not pairs, so which product belongs to which vendor is not something this page can say.

Vendors (1)

concrete cms

Products (1)

concrete cms

Every base score collected

Sources score independently and disagree; each row says who scored it and under which version.

Score	Version	Severity	Expl.	Impact	Source
7.2	CVSS 4.0	HIGH	—	—	cvelistV5

Weakness & attack patterns

CWE-862

Attack patterns reported against this CVE. The ATT&CK techniques below are inferred from its weakness class.

T1211Exploitation for Defensive Evasion
T1542.002Pre-OS Boot: Component Firmware
T1556Modify Authentication Process

Detection

Read off the CVSS vector and the weakness class. Starting points, not rules we have tested.

Search application, proxy, and WAF logs for requests touching /ccm/api/1.0/pages/, /AV:N/AC:L/AT:P/PR:H/UI:P/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N.

References

1 on the record

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

Elsewhere on this site

concrete cmsevery CVE for this vendor
CWE-862other pages naming this weakness

Not in any source we poll

Listed rather than left blank: an empty field and an unmeasured one look identical on screen, and only one is a reason to look elsewhere.

No confirmed IOCs, IP addresses, domains, file hashes, or malware artifacts supplied.
No organization-specific asset inventory, compensating-control status, or patch deployment evidence supplied.
No exploit packet captures, log samples, or incident case IDs supplied.