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CVE-2026-8340

21
FAUCET Score

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an attacker-chosen previously-uploaded version (downgrade to an older version of a file, or activation of a co-editor's unpublished version).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.

First published: May 22, 2026Last modified: May 22, 2026

Impacted Technologies

VendorProductVersion(s)CPE
< 9.5.1CPE matchmatch criteria
cpe:2.3:a:concretecms:concrete_cms:*:*:*:*:*:*:*:*
>= 5.0, <= 9.5.0CPE match
cpe:2.3:a:concretecms:concrete_cms:*:*:*:*:*:*:*:*

CVSS Data

CVSS version used by this source: 4.0

2.3LOW

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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

Attack Vector
NETWORK
Attack Complexity
LOW
Attack Requirements
PRESENT
Privileges Required
NONE
User Interaction
PASSIVE
VS Confidentiality
NONE
VS Integrity
LOW
VS Availability
NONE
SS Confidentiality
NONE
SS Integrity
NONE
SS Availability
NONE
Exploit Maturity
NOT_DEFINED
CvssVersion
4.0

Exploit Intelligence

EPSS Score
0.10%
Probability of exploitation in next 30 days
EPSS Percentile
1.1%
Percentile rank of EPSS score among Peer Group
As of 2026-07-27
Model: v2026.06.15
This CVE's current EPSS score of 0.0010 is in the 0th percentile among its peer group of 26,234 CVEs.

Social Chatter

No social media mentions found for this CVE.

The average CVE in this peer group has 0.0 Twitter, 0.0 Reddit, 0.1 Bluesky, 0.0 Mastodon, and 0.1 GitHub mentions.

Media Mentions

No media coverage found for this CVE.

The average CVE in this peer group has 0.1 InfoSec Media, 0.0 Vendor Blog, and 0.0 Security Researcher mentions.

Remediation

Patch Available

Vendor Patches (1)

composerpatch availablevia ghsa
Product: concrete5/concrete5Fixed in: 9.5.1

Vendor Advisories (1)

composerGHSA-xjg6-5v39-v7fclow

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

May 26, 2026

References

documentation.concretecms.org / 9-x/developers/introduction/version-history/951-release-notes
Release Notes