CVE-2026-8340 PUBLISHED

Concrete CMS 9.5.0 and below is vulnerable to CSRF via Backend\File::approveVersion

Assigner: ConcreteCMS
Reserved: 11.05.2026 Published: 22.05.2026 Updated: 22.05.2026

Concrete CMS 9.5.0 and below is vulnerable to CSRF via Backend\File::approveVersion. Victim with edit_file_contents permission is CSRF'd into publishing an attacker-chosen previously-uploaded version (downgrade to an older version of a file, or activation of a co-editor's unpublished version). The Concrete CMS security team gave this vulnerability a CVSS v.4.0 score of 2.3 with vector CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:P/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N. Thanks Winston Crooker for reporting.

Metrics

CVSS 4.0

CVSS Vector: CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:P/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N
CVSS Score: 2.3

Exploitability Metrics		Vulnerable System Impact Metrics		Subsequent System Impact Metrics
Attack Vector	Network	Confidentiality	None	Confidentiality	None
Attack Complexity	Low	Integrity	Low	Integrity	None
Attack Requirements	Present	Availability	None	Availability	None
Privileges Required	None
User Interaction	Passive

CVSS 4.0

Product Status

Vendor	Concrete CMS
Product	Concrete CMS
Versions	Default: unaffected affected from 5.0 to 9.5.0 (incl.)

Credits

Winston Crooker finder

References

https://documentation.concretecms.org/9-x/developers/introduction/version-history/951-release-notes

Problem Types

CWE-352 Cross-Site request forgery (CSRF) CWE

Impacts

CAPEC-62 Cross Site Request Forgery
CAPEC-60 Reusing Session IDs (aka Session Replay)