PatchTheCVECVE-2026-8340: Concrete CMS 9.5.0 and below is vulnerable to CSRF via Backend\File::approveVersion. Victim with edit_file_con
CVE-2026-8340 is a medium-severity flaw (CVSS 4.3) affecting concrete cms. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.
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an attacker-chosen previously-uploaded version (downgrade to an older version of a file, or activation of a co-editor's unpublished version).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:
Why this priority
- No elevated risk signals yet
A fixed release or distro patch exists.
Risk facts
| CVSS score | 4.3 (Medium) |
| Attack vector | Network (remote) |
| Attack complexity | Low |
| Privileges needed | None |
| User interaction | Required |
| EPSS exploit chance | 0.1% (top 99%) |
| CISA exploited list | No |
| Weakness | CWE-352 |
| Published | 2026-05-22 |
| Last modified | 2026-07-23 |
Last updated 2026-07-23 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score
Am I affected?
Timeline
- Published CVE record published
- Updated Record last modified
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.
Quick answers
How do I fix CVE-2026-8340?
concrete cms: upgrade to 9.5.1. Exact commands for each OS are on this page.
Is CVE-2026-8340 being exploited?
CVE-2026-8340 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.
What does CVE-2026-8340 affect?
CVE-2026-8340 affects concrete cms. Severity is medium (CVSS 4.3). 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
How urgent is CVE-2026-8340?
Priority 15/100. No elevated risk signals yet.
Related CVEs
- CVE-2026-18111 MEDIUM 6.1 UPGRADE Concrete CMS 9 before 9.5.3 was vulnerable to stored cross-site scripting (XSS) in the Feature, Feature Link,
- CVE-2026-18117 MEDIUM 5.4 UPGRADE Concrete CMS 9.0.0 through 9.5.3 is vulnerable to stored XSS via the custom page alias name (customAliasName)
- CVE-2026-68526 MEDIUM 4.3 UPGRADE Concrete CMS before 9.5.3 did not validate an anti-CSRF token in the Calendar event duplicate dialog controlle
- CVE-2026-81912 MEDIUM 5.7 UPGRADE Concrete CMS before 9.5.3 is vulnerable to Cross-Site Request Forgery in the Move Multiple Groups feature
- CVE-2026-81913 MEDIUM 6.1 UPGRADE Concrete CMS versions 9.5.0 through 9.5.2 are vulnerable to Open Redirect via the rcURL parameter