File-version publication via missing CSRF validation
Published May 22, 2026 · Updated May 22, 2026
Cross-site request forgery in Backend\File::approveVersion in Concrete CMS 9.5.0 and earlier allows remote attackers to publish a file version. The backend action approves an attacker-selected, previously uploaded version without validating an anti-CSRF token. Exploitation requires a logged-in victim with edit_file_contents permission to follow attacker-controlled content, enabling a downgrade to an older file or publication of a co-editor's unpublished version.
Summary
What happened
Cross-site request forgery in Backend\File::approveVersion in Concrete CMS 9.5.0 and earlier allows remote attackers to publish a file version. The backend action approves an attacker-selected, previously uploaded version without validating an anti-CSRF token. Exploitation requires a logged-in victim with edit_file_contents permission to follow attacker-controlled content, enabling a downgrade to an older file or publication of a co-editor's unpublished version.
The record
- CVE
- CVE-2026-8340
- Published
- May 22, 2026
- Updated
- May 22, 2026
- Vendor
- Concrete CMS
- Product
- Concrete CMS
- Classifications
- CWE-352, T1204.001
- Attack vector
- network
- Privileges
- unauthenticated
Timeline
How it unfolded
- May 22, 2026CVE publishedPublication date reported by the CVE source.
- May 22, 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?
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- Affected versionversion=5.0 <=9.5.0
What conditions does exploitation require?
What is affected?
Published CVSS scores
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Attacks
What attackers are doing with it
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Public exploit references
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Technologies
Your stack
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Your stack
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