Unauthorized form modification via block-agnostic CSRF token
Published Sep 15, 2026 · Updated Sep 15, 2026
Missing authorization in the Express Form block in Concrete CMS 9.0.0 through 9.5.2 allows remote authenticated users to alter forms. Control-management actions validate a user-and-action CSRF token but omit a permission check for the targeted block, page, or form. Edit access to one Express Form supplies a reusable token for unauthorized control changes, including stored HTML script injection that executes when rendered.
Summary
What happened
Missing authorization in the Express Form block in Concrete CMS 9.0.0 through 9.5.2 allows remote authenticated users to alter forms. Control-management actions validate a user-and-action CSRF token but omit a permission check for the targeted block, page, or form. Edit access to one Express Form supplies a reusable token for unauthorized control changes, including stored HTML script injection that executes when rendered.
The record
- CVE
- CVE-2026-18426
- Published
- Sep 15, 2026
- Updated
- Sep 15, 2026
- Vendor
- Concrete CMS
- Product
- Concrete CMS
- Classifications
- CWE-862
- Attack vector
- network
- Privileges
- authenticated
Timeline
How it unfolded
- Sep 15, 2026CVE publishedPublication date reported by the CVE source.
- Sep 15, 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.
- Affected versionversion=9.0.0 <=9.5.2
What conditions does exploitation require?
What is affected?
Published CVSS scores
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.
Weakness, pattern, technique
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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