CVE-2026-81901Network attack vectorHinoki check available

Stored XSS via unauthorized page attribute update

Published Sep 14, 2026 · Updated Sep 14, 2026

Stored XSS in Concrete CMS 9.2.0 through 9.5.2 allows remote authenticated users to execute JavaScript in visitors' browsers. The REST API page update endpoint omits property, template, and type authorization and stores header_extra_content for unescaped insertion into every page head. A user needs only page content-editing rights, and execution occurs when any visitor, including a higher-privileged reviewer, loads the affected page version.

CVSS severity7.2
High
EPSS probability0.33%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkAvailable
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Summary

What happened

Stored XSS in Concrete CMS 9.2.0 through 9.5.2 allows remote authenticated users to execute JavaScript in visitors' browsers. The REST API page update endpoint omits property, template, and type authorization and stores header_extra_content for unescaped insertion into every page head. A user needs only page content-editing rights, and execution occurs when any visitor, including a higher-privileged reviewer, loads the affected page version.

The record

CVE
CVE-2026-81901
Published
Sep 14, 2026
Updated
Sep 14, 2026
Vendor
Concrete CMS
Product
Concrete CMS
Classifications
T1189
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Sep 14, 2026CVE publishedPublication date reported by the CVE source.
  2. Sep 14, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=9.2.0 <=9.5.2

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

Concrete CMS · Concrete CMSversion=9.2.0 <=9.5.2

Published CVSS scores

7.2Concrete CMS security teamCVSS:4.0/AV:N/AC:L/AT:P/PR:H/UI:P/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

T1189Drive-by Compromise

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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